Rename class and methods in tensors on free modules.

The renaming is
FreeModuleEndomorphism --> FreeModuleEndomorphismTensor
FreeModuleAutomorphism --> FreeModuleAutomorphismTensor
FreeModuleIdentityMap --> FreeModuleIdentityTensor
Methods of FiniteRankFreeModule:
- endomorphism() --> endomorphism_tensor()
- automorphism() --> automorphism_tensor()
- identity_map() --> identity_tensor()
- endomorphism_map() --> endomorphism()
- identity_morphism() --> identity_map()