WIP: Build python2 and python3 rpms

This merge updates the spec file for all sub-packages to provide two python packages, as follows:

• python2-<> - bindings for python2.x (2.7 on centos7)
• python3x-<> - bindings for python3.x (3.4 on centos7)

Note that this renames the python2 packages from <>-python to match the naming convention for fedora. I have attempted to add the correct combination of Provides, Conflicts, and Obsoletes such that downstream dependents don't have to modify their spec straight away.

The %build and %install steps look a bit hacky to me, mainly because you have to re-%configure for each version of python, so @adam-mercer should give this a thorough review before merging.

Fixes #37 (closed).