create a useful pointer to the running rapp in the manager while it runs.
fix stop app for naturally terminating apps, fixes #31. Also fixes #30.
better errors messages for stop app, closes #32.
Merge pull request #35 from robotics-in-concert/stop_app_fix

Stop app fixes
return values from error status was wrong
legacy code, unused now.
Merge branch 'hydro-devel' into multi-hub