Tags+Collections can be added to Units

[bradenmacdonald]

Allow tagging units with tags, including adding/removing tags.

Allow adding units to/from collections in the same sidebar, just as it works for components.

Add this to the "Organize" tab of the blank sidebar from #1617

[bradenmacdonald]

@jmakowski1123 @sdaitzman I added this story to Epic 12 as requested by @jmakowski1123 so that we'll have it for Teak.

Question: should we also implement "Add Unit to Collections" on the sidebar, or just tags?

[jmakowski1123]

Yes, also add Add units to collections please!