Editor entity blocks

[AllyTally]

Changes:

Activity zones are pretty hardcoded, so this makes them data-driven instead, using the edentity system. This is, once again, laying foundation for the goal of reducing the split between custom levels and the main game.

Activity zones are ID 20, and rendered the same as script boxes. This adds activitytext and activitycolour properties to editor entities.

EDIT: This PR now has edentities for every block type. 21 are collision boxes, 22 are damage boxes, 23 are directional boxes and 24 are safe boxes.

Legal Stuff:

By submitting this pull request, I confirm that...

• [x] My changes may be used in a future commercial release of VVVVVV
• [x] I will be credited in a CONTRIBUTORS file and the "GitHub Friends" section of the credits for all of said releases, but will NOT be compensated for these changes

[AllyTally]

I've now added a createblock command, since I realized that activity zones should have the ability to be conditional -- and activity zones should be able to spawn themselves. The main game does both of these!