StruphyModels base class
- Small fixes in doc.
- Fix argument for example_pproc.
- The time step dt must be given to call in schur solver. This allows for any splitting method to be defined later.
- Change space_cont to space_id, add set_initial_conditions method to Field_init.
- Remove some tests from test_psydac_basics.py mapping test.
- Added new file including StruphyModels base class and, as first example, Maxwell class.
- Adapt maxwell_psydac to StruphyModels base class.