ENH: html facelift for SceneViews

Implemented a Qt web view and populated it with HTML to allow
viewing, editing, restoring, creating scene views with the
layout requested.

The scene view thumbnail is being written to disk in a temp dir.
To get the Edit, Delete, Restore and Capture funtionality I'm capturing the
clicks on the links and parsing specially formatted urls
(Edit/Restore/Delete mrmlNodeID/Create)

Clear out the temp files on scene close and clear the memory cache, now
don't have to write them out all the time. Resize the images before
writing to disk so that the web view doesn't have to handle resizing.
Added in support for VTK6
Created new MRML web view based on the qMRMLChartView.
It allows better resizing (returns an invalid size hint,
sets size policy to expanding/expanding) so that the web
view doesn't keep getting reset to width = 800.
Added a plug in for the designer.
Save and restore the scroll position so user goes back
to the scene view node that they were previously viewing after
adding a new scene view.

Running on a mac, you can't see the scroll bar
on the data store page nor on the scene views
module widget, but it is visible on a linux build.
You can scroll using the trackpad and it is consistent,
so only show the scroll bar as needed.
The dialog superclass disables capturing a new
thumbnail on review/edit so don't resave the thumbnail type nor the image data.

Issue #1299

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23160 3bd1e089-480b-0410-8dfb-8563597acbee