Node to insert dialogue sentences into datacentre in new collection
First version of idle behaviour for robot.
Still needs:
* Testing
* Incorporation of engagement check
 * Reaction to engagement
* PTU turning when error is fixed.
* Create engagement action server to handle interaction after engagement was detected
* Incorporated engagemant_checker in the system to trigger engagement_server
* Moved magic numbers to parameters
* Moved some output to debug level
* Moved setting of voice for mary to top level server
Merge pull request #31 from cdondrup/hydro-devel

First version of the idle behaviour used prior to the game play to engage people with the robot.