MonsterPropertiesWindow

At last, I've got a first working sketch of the 'monster properties window'. It turned out quite tricky to get it working. It can report whether gobs have links and initialization expressions in addition to tehir class. There still is plenty of work, like being able to actually update state when you use the widgets, and write an expression by using the customized 'TypeWord' widget featuring the full gobscript characters set.

Trickiness came from window-to-window communication, so that the right widgets got displayed at the right time (having to hide the whole "tileset" widgets)