Clean up
- updated license
- updated build-backend to hatchling
- fixed sphinx issues
- reader outputs masked arrays if needed now
- reader was optimized in performance (reading recreated info/grid for each update call)
- minor internal refactoring
- made examples work again
- added writing of variable attributes from
Info.meta - fixed reading of axes attributes to
Grid.axes_attributes - reworked Layer mechanics in !38 (merged)