Clean up handling of layout padding

[cdyk]

Tinia jobs often have a lot of nested layouts. At least in the QTcontroller, these layouts defaults to 11px padding each, leaving GUI's with a lot of blank space.

Adding foobar_layout->setContentsMargins( 0, 0, 0, 0 ) removes a lot of this space, however, some space is usually desirable. So the GUI needs to flag that it wants some space here or there or the layout is just to organize stuff.

One approach is to have no margins at all, and force the job to add 'spacer widgets' to create padding where desired.

Another approach is to add a flag on the layout element as to whether or not this layout should pad its contents.

However, it needs to work cleanly with the Dojo-based GUI builder.