interactivemarkers: get the correct transformation for sub-markers

tested with http://www.cse.wustl.edu/~dvl1/stuff/marker_marker_marker_frame_bug.zip - submarker now shows up where you'd expect it to
also made sure examples/interactivemarkers.html still works
use a separate TFClient to get the transform from InteractiveMarker to its sub-Markers
add support for MarkerArray topic

MarkerClient will now automatically subscribe to the topic provided in the constructor, *and* <topicname>_array
use namespace for Markers - ID alone is not supposed to be unique
move marker array client functionality to its own class
change comments
Merge pull request #74 from T045T/marker_array

MarkerClient: Subscribe to MarkerArray topic
fix copy-paste error
Merge pull request #72 from T045T/interactive_marker_submarker_pose

interactivemarkers: get the correct transformation for sub-markers
prevents empty text from being rendered
Merge pull request #76 from rctoris/develop

prevents empty text from being rendered
0.9.0
0.10.0-SNAPSHOT
Removed outdated link.