Adds capabilities support for the app manager

New features:
* The app manager retrieves information about available capabilities from the capability server.
* Rapps with unmet capability dependencies are pruned from the list of runnable rapps.
* The app manager communicates with the capability server to start and stop capabilities as needed.
* The app manager applies remappings required for the capabilities automatically.

For the app manager to work rocon_msgs' PR 48 (https://github.com/robotics-in-concert/rocon_msgs/pull/48) needs to be merged as well.

All changes are (should be) back-wards compatible, i.e. current and new rapps are not forced to use capabilities.