Qtfred visual tweaks

[MjnMixael]

Went in to make do some UI polish, ended up fixing a few things, too.

• Variables and Containers in their widget now color their rows based on type (string/number or list/map) to make it easier to tell at a glance what type each on in the list is.
• Props and Jump nodes were added to the visibility filters along with Ships, Waypoints, and Player Starts.
• The goals dialog was refactored to be dynamically built. The number of rows will now match MAX_AI_GOALS and in testing this I found a whole host of issues with saving/loading data for orders that I fixed up here, mostly regarding subsystems and docking bays being selected.