Catkin conversion, preparing for Groovy and Hydro releases

*Should not be merged until after axis_camera-0.0.2 release to Fuerte.*

I marked this as axis_camera-0.1.0, to begin a new major.minor.patch sequence. Change that, if desired.

Also adds README.rst and CHANGELOG.rst. 

Builds docs with Sphinx, but without any documentation embedded in the Python scripts yet.