Fixed|PopupWidget: Stop observing parent’s deletion when popup closed
libdeng2|Refactor|CommandLine: Checking for command line options with parameters

Added a more convenient way to get all the parameters of a command
line option in one call.
UI|Style: Added “-fontsize” option to change font sizes

This is a temporary solution to the Rift UI font sizing. One needs
to manually specify a suitable font size (e.g., “-fontsize 1.5”).

The correct way would be to create an alternative UI style pack for
the Rift and allow switching UI styles on the fly. That will need
some additional work, though, as all widgets are not prepared for
dynamic UI style changes.