Support full width regions on workbench_moderation drafts

When using workbench_moderation with a panelized node that has a full width region, the full width region will display correctly on the published version, or the draft if there is no published version. However, if there is a published version, then viewing the draft will display the full width region incorrectly.

The problem is in the way that mvpcreator_theme determines if the Panels display being rendered should be rendered full width. One of the tests it does to make sure the Panels display being rendered is the outer-most one (as opposed to, say, a mini Panel inside it), and it does that by loading the Panels configuration for the page and getting the display it thinks should be rendered based on that configuration, and then compares the did of that with the Panels display being rendered.

The problem is that by looking at the Panels configuration it gets the published Panels display, but the display getting rendered is different, it's the one associated with the draft. So, somehow it needs to see that workbench_moderation is involved and that we're on a draft page and grab the draft display instead (in mvpcreator_theme_current_panels_variant()).