Added progress dialog.

Problems with how ParaView fires progress now become obvious. We need to
cleanup ParaView's progress reporting infrastructure and this will start
working better.
Adding ModulePropertiesPanel.

Added properties panel for modules. This adds a mechanism for each
module to show relevant properties in the ModulePropertiesPanel.

Also added support for deleting modules.
Added ability to toggle module visibility.

PipelineWidget now has 2 columns, the new one is used for showing
eyeballs for visibility.
Updates to build with ParaView/master.
Add splitter to the central widget.
Fixed PipelineWidget column sizes.

The eyeball is now placed on the left to avoid needing to scroll the
widget to change visibility.
Added module for orthogonal slicing.
Added support for color map editor on Volume/Slice modules.
Merge branch 'master' into dax-contour
Update the Contour Module to the new Module API.
The implementation of caching streaming workers doesn't work, back it out.
Don't use dax to compute back world ijk, as it can't handle negative extents.
Re-implement SubdividedVolume constructor to fix subgrid extent bugs.
StreamingWorker can now be canceled, also fixed threading concurrency issue.

If the StreamingWorker finished contouring before the REQUEST_STREAMING_UPDATE
call to the representation had occurred we would enter a state where we never
fetch the computed polydata but always have empty output. For now
we state we are never finished to solve the problem, but I expect in the long
term we will need a different solution.