* FEM: remove calculix from solvers
* FEM: remove calculix from joint with ccxtools if branches
* FEM: remove calculix from its if
* FEM: fix cxx typo in translations
* FEM: fix cxx typo in classes name
* FEM: fix ccx typo in shortcuts
* FEM: convert FEM_*CcxTools to CamelCase
* FEM: remove tests related to calculix
* FEM: remove test_solver_calculix.py from Fem/CMakeLists.txt
* FEM: convert all 'CalculiXccxTools' to 'CalculiXCcxTools'
* FEM: revert changes in all *_*.ts files
* FEM: convert 'SolverCcxtools' to 'SolverCcxTools'
* FEM: convert remaining 'Ccxtools' to 'CcxTools'
- add addGroup, addGroupElements, removeGroup to C++ mesh class
- expose the methods to Python
- add a unit test class
- update test commands file
- add test to fem test app module