Support ColorAttributeType.

First pass a supporting ColorAttributeType for Python. We can do better.
Need to figure our paraview.compatibility to better support
getting/setting ColorAttributeType and ColorArrayName.

Change-Id: I18aec119f43a6f92c9e7fa7e172a75c7fc8ae1d3
Merge topic 'lookup_table_cleanup' into next

38f30773 Support ColorAttributeType.