[Paraview-developers] Making paraView dev life easier with custom app

[Utkarsh Ayachit]

>  - helping show data without using ApplyBehavior and pqPropertiesPanel

I think the easiest solution for this would be simply make
pqApplyBehaviour independent of pqPropertiesPanel. The code may need
some restructuring, but essentially, there are two things that are
happening here:

1. do tasks on applying a single filter/source
2. do tasks after all sources/fitlers are applied.

Adding API on the class to provide access to these two functions in a
pqPropertiesPanel independent way may be the way to go.