fixes for indicate scene idx to use for scene editor
fixes lesson loading and rendering

- speeds up loading of lesson metadata for home screen
- progressively loads lessons so user can start once first is loaded
- requires lesson to be completed before opening next one
- tunes lesson rendering html
shrunk the new activity form a little bit
Merge branch 'sprint5-lesson-tuning' of github.com:n8fr8/mrapp into sprint5-lesson-tuning