Cross-link docs from sphinx to doxygen
Remove doc/source/user_manual/reference.rst (was empty)
Bundle rawfiles Sphinx directive for docs build
Move doc/html/doc to doc/source/fhelp
Add tools_reference.rst page
Move images from doc/html/images to doc/source/_static
Move images from test to doc/source/_static
Move ctools.css file from doc/html to doc/source/fhelp
Remove old HTML docs pages that have been transferred to RST
Add doc/html to .gitignore

The html output folder should only contain generated files,
so that it becomes possible to clean the docs build via
`rm -r doc/html`.
Add intersphinx_mapping to gammalib
Move ctools.i into ctools/ctools.i
Build ctools.py in ctools directory
Add __init__.py file for ctools
Movve obsutils.py to pyext/ctools/obsutils.py
Import obsutilis in ctools
Remove obsutils rule from scripts
Fix configures and python test
Add an depracted obsutils.py in its previous location
Update the gitignore rules