Refactoring: depend on FORCES

This repo could be modified to use FORCES as a dependency.

Needed changes:

• solve #8 (closed)
• add mo_integrate, mo_kernel and mo_nelmin to FORCES (chs/forces!42 (merged))
• add to mo_utils in FORCES:
  • linspace
  • iminloc
• only keep the following files in src/:
  • InputOutput.f90
  • Main.f90
  • mo_drought_evaluation.f90
  • mo_global_variables.f90
  • mo_read.f90
  • mo_smi_constants.f90
  • mo_smi.f90
• use structure of Fortran-Template
  • add cmake subrepo
  • add hpc-module-loads subrepo
  • cleanup cmake files and use CPM (package manager) to include FORCES
  • update gitlab-runner
  • (nice to have) copy docs structure form Fortran-Template
  • (nice to have) copy check-case runner structure from mHM