catalyst steering

Add support for catalyst-live steering.

• Config XML looks like this:

<sensei>
  <analysis type="catalyst" pipeline="pythonscript"
    filename="@CMAKE_CURRENT_SOURCE_DIR@/oscillator_catalyst_steering.py" enabled="1"
    plugin_xml="@CMAKE_CURRENT_SOURCE_DIR@/oscillator_catalyst_steering_proxies.xml">
    <result steerable_source_type="Oscillators" mesh="oscillators" />
  </analysis>
</sensei>

• plugin_xml helps add new proxy definitions (which in turn help ParaView build the UI for steering).
  

Demo

Here's a video with Live + Oscillators in action.

Depends on paraview/paraview!3863 (merged)