Feature Release

This release begins the migration of "challenge" features from GameEngine into TopoMojo. As a minor revision, it includes database migrations; always a good idea to ensure a recent database backup before updating.

Workspace authors can associate a set of challenge questions with a topology, and submit them for grading.
They can also specify various "randomization macros" for guest settings and question answers, providing for "infinity" style labs (different variant with every launch).

Also added a special network name _none_ which will disconnect the virtual interface to which it is applied.