Integrate Trilinos documentation into Fortran code

[sethrj]

• [ ] Export Trilinos Doxygen as XML
• [ ] Convert XML to SWIG .i file with doxy2swig
• [ ] Modify .i file as needed
• [x] (in SWIG fortran) add support for %feature("autodoc")

[aprokop]

The way PyTrilinos currently works:

• In $PYTRILINOS_DIR/CMakeLists.txt it configures PyTrilinos_DOCSTRINGS (there are a few errors in it, though)
• In $PYTRILINOS_DIR/docs/Doxygen it a) generates helpers scripts from .in files using CONFIGURE_FILE command; b) Runs Doxygen for the specified packages to produce XML files; c) Runs doxy2swig file on those XML files to produce .i files with docstrings (which are stored in the binary directory/docs/Doxygen
• In $PYTRILINOS_DIR/src it a) includes that Doxygen binary directory; b) Add -I option to running swig so that it can pick up those files; and c) manually includes the docs files (*_dox.i) into the proper package files (like Epetra.i).

[aprokop]

We need to copy this machinery from PyTrilinos, updated with a more recent version of doxy2swig (including @mattbement 's changes to include meta-data) and put it in ForTrilinos.