Merge strategy of recent PRs

[krystophny]

To simplify reviews and discussion here is a summary of the recent PRs, and a proposed merge order:

• - Docstring #230 - changes
• - Return array #231 - changes
• - Type check #232 - changes
• - Several interface for one procedure #238 - changes
• - Fortran object oriented support #239 - changes
  • - Fortran oo support with unittest #243 - changes
• - Fix #235 allocatable classes #236 - changes
• - Fix #41 abstract classes #233 - changes

(I rebased #236 and #233 on #239 and applied all patches in order onto master on https://github.com/itpplasma/f90wrap for testing.)

• Finally, since Fix issue 157 #158 is stale some time now - should it be merged or discarded?

[jameskermode]

Thanks @krystophny, very useful to have a rationalised TODO list. I'll try to use the start-of-the-year lull to get through this. Agree #157 is stale and should be discarded, that's the easiest one so have done immediately.

[jameskermode]

First few are merged but I'll hold off here pending a decision on removing pytest dependency from #239 and resolution of the CI failures in #242

[krystophny]

Removed the dependency in #243 , and noticed #242 only now. I have a quick look also there.