Add some more fixes for python3
More fixes for Python3
More Python3 fixes.
  -- Also added dolfin.__pythonversion__ so one can check dynamically what python version the
     extension modules was compiled with. It is not used for anything yet.
Small typo fix
Revert change to detecting swig version.
Revert changes to swigversion generation
Merge branch 'johanhake/python3-fixes'