Changes needed to run the 4.3 css theme based UI in Kepler

Changes the RMAP to appoint the Kepler simultaneous release and
the 4.3 Eclipse platform. Specific entry for egit/jgit was removed.

Also adds a cssTheme property to product extension point. Needed
to overcome https://bugs.eclipse.org/bugs/show_bug.cgi?id=385572
Fix problem with re-added module missing the Puppet Nature

This commit inserts a check to see if the target directory for a new
project is empty. The user is asked to confirm an overwrite when it
isn't. The directory is emptied prior to creating the new project if
the user confirms which means that no old .project file can be
lingering and screw up the creation of a new project.

Closes #528
Merge branch 'master' into kepler
Merge branch 'dev' into kepler
Merge branch 'dev' into kepler
Merge branch 'dev' into kepler
Add Kepler update sites to the configuration instructions
Merge branch 'dev' into kepler
Merge remote-tracking branch 'origin/dev' into kepler
Change Copyright holder, feature provider, and licensor to Puppet Labs
Merge branch 'dev' into kepler
Merge branch 'kepler' into puppetlabs-copyright
Merge branch 'dev' into kepler
Bump Geppetto version to 4.0.0
Remove Juno specific version constraints

Some version constraints that was needed to overcome discrepancies
in the Juno release train are removed by this commit since they
are no longer needed when using the Kepler platform.
Merge branch 'kepler' into puppetlabs-copyright