KnowRob GitHub repository structure

The catkinized KnowRob version is used by the IAI group in Bremen for more then 6 months. For this summer, we plan the next KnowRob release based on the catkinized version that proved to be stable in the last months.

The development was done in the 'indigo-devel' branch at GitHub while the 'master' branch contained the rosws-based KnowRob version. In order to avoid confusion, we decided to restructure the GitHub repository so that the code is actively developed in the master branch again with different branches for different supported ROS versions. The old 'master' branch has moved to a new branch 'groovy'. Note that this KnowRob version is not actively developed anymore. The old 'indigo-devel' branch has moved to the 'master' branch. Additionally, we mirrored the new 'master' branch to new branches 'hydro' and 'indigo' which contain the latest stable snapshot for the corresponding ROS version.