Replace Interactive Snapshot with Compressed Depth Cloud in rviz IM frontend

[mateiciocarlie]

After #30 is complete, rviz will allow the user to interact with any scene component. At that point, there is no more need for the Interactive Snapshot (IS), which is a bandwidth-hog.

Use the new interaction tools in #30 applied to the Compressed Depth Cloud (CDC) to provide all the functionality currently provided by the IS.

While the IS is low-bandwidth, we'd still like the ability to

• Pause Streaming
• Resume Streaming
• Refresh
  on demand. Build an rviz display plugin that provides this functionality by talking directly to the CDC publisher and sending the commands above. Note that this display will not talk directly to the CDC rendering display within rviz.