Implement default metadata for components and adapters

This implements default metadata as specified in landtrans/landtech/management#233

@muellese Should we somehow try to get the actual slot metadata (like units, grid, ...) into here too? Not sure how to represent grids, but it could IMO be useful.
Done.

TODO:

• Update docs
• Add book section
• Overwrite/implement for existing components and adapters
• Update CHANGELOG
• Merge !273 (merged)

Example

{'adapters': {'Scale@2391719058640': {'class': 'finam.adapters.base.Scale',
                                      'in_info': {'grid': 'NoGrid (0D)',
                                                  'units': ''},
                                      'name': 'Scale',
                                      'out_info': {'grid': 'NoGrid (0D)',
                                                   'units': ''}},
              'Scale@2391719059168': {'class': 'finam.adapters.base.Scale',
                                      'in_info': {'grid': 'NoGrid (0D)',
                                                  'units': ''},
                                      'name': 'Scale',
                                      'out_info': {'grid': 'NoGrid (0D)',
                                                   'units': ''}}},
 'components': {'MockupComponent@2391719110688': {'class': 'test_schedule.MockupComponent',
                                                  'inputs': {},
                                                  'name': 'MockupComponent',
                                                  'outputs': {'Output': {'class': 'finam.sdk.output.Output',
                                                                         'has_targets': True,
                                                                         'info': {'grid': 'NoGrid (0D)',
                                                                                  'units': ''},
                                                                         'is_static': False,
                                                                         'name': 'Output'}}},
                'MockupDependentComponent@2391719111408': {'class': 'test_schedule.MockupDependentComponent',
                                                           'inputs': {'Input': {'class': 'finam.sdk.input.Input',
                                                                                'info': {'grid': 'NoGrid (0D)',
                                                                                         'units': ''},
                                                                                'is_static': False,
                                                                                'name': 'Input'}},
                                                           'name': 'MockupDependentComponent',
                                                           'outputs': {}},
                'MockupDependentComponent@2391719111696': {'class': 'test_schedule.MockupDependentComponent',
                                                           'inputs': {'Input': {'class': 'finam.sdk.input.Input',
                                                                                'info': {'grid': 'NoGrid (0D)',
                                                                                         'units': ''},
                                                                                'is_static': False,
                                                                                'name': 'Input'}},
                                                           'name': 'MockupDependentComponent',
                                                           'outputs': {}}},
 'links': [{'from': {'component': 'MockupComponent@2391719110688',
                     'output': 'Output'},
            'to': {'adapter': 'Scale@2391719059168'}},
           {'from': {'component': 'MockupComponent@2391719110688',
                     'output': 'Output'},
            'to': {'component': 'MockupDependentComponent@2391719111696',
                   'input': 'Input'}},
           {'from': {'adapter': 'Scale@2391719058640'},
            'to': {'component': 'MockupDependentComponent@2391719111408',
                   'input': 'Input'}},
           {'from': {'adapter': 'Scale@2391719059168'},
            'to': {'adapter': 'Scale@2391719058640'}}],
 'time_frame': [datetime.datetime(2000, 1, 1, 0, 0), None]}

docs/source/finam-book/development/data_metadata.rst

@@ -256,3 +256,14 @@ Metadata flow
 
 For details on how metadata is provided, and how it is passed around during coupling,
 see chapter :doc:`./connect_phase`.
+
+
+Composition metadata
+--------------------
+
+Besides metadata for data exchange, FINAM provides functionality to access metadata that describes a given :class:`Composition` and corresponding simulation.
+Users can call :attr:`Composition.metadata` to retrieve a nested `dict` of all metadata.
+This encompasses general metadata like the simulation time frame, as well as metadata for individual components and adapters and the coupling links.
+
+:class:`Component` as well as `Adapter` provide default implementations of :attr:`Component.metadata` and :attr:`Adapter.metadata`, respectively.
+Developers can overwrite these properties to add their own specific metadata. For examples, see the API docs for :attr:`Component.metadata` and :attr:`Adapter.metadata`.