Updated Doxyfile

Following changes were made:
Relative path in input dir
Set xml doc generation to YES (dependency for breathe)
Updated paths for xmldoc
Adding sphinx support

Added a conf file. Basic version.
Should be updated in later version.
Updated conf.py for breathe extension
Updated comments in `basic.h` to be recognised by `breathe`

Added `doc/src/basic.rst` to document the basic class.
Index linked to this file.
`autodoxygen` directive of breathe is broken.
Will have to set up a script for automationin case
things don't pane out.
Posted on an existing issue to check if issue can be fixed.
Merge pull request #121 from sushant-hiray/documentation

Added breathe documentation