Split Homescreen app into subfolder

[dedmen]

• Split Homescreen out into separate app
• Add infrastructure to have apps in subfolders/addons
• Added onClose events for apps (so they can clean up after themselves)
• Make homescreen use a controls group to store apps (so we can delete everything at once)

Todo:
The phone itself should create a "app-area" controls group.
After app is closed, the phone should clear that area (in case any app leaves something behind or doesn't implement onClose properly)
When an app is opened, pass only the appArea to it, it can then create its contents right into the appArea.
Then we also don't need to specify phone height/width, because the app can read the size of the appArea, and its easier for us to change the size.