libdeng2|Debug|IndirectRule: More concise description
Fixed|libappfw: De- and re-initializing procedural images
Fixed|libappfw|MenuWidget: Take padding into account in layout

Also added a helper template method for getting widgets representing
items.
libappfw|FoldPanelWidget: Fold title must be manually created

Previously the title button would be created but never deleted, if
it was unused.
Fixed|libappfw|Margins: Updating margins

The sum of the left and right margins wasn't always updated properly.
libappfw|GridLayout: Added method for querying the layout's paddings
UI|Ring Zero: Revised game selection menu

The game selection menu is now divided into foldable subgroups.
Incomplete games are put in a separate group.

Changed the layout of the menu so that items have a fixed height
regardless of view size. The number of columns still changes
depending on view width, though.