Mission Object HUD

- Added the mission objective HUD element
- Added objectives to all of the scenarios
- Removed unused method declarations
- Removed unused inventory HUD code
- Removed unused minirover HUD code
- Improved camera angle in scenario 3a

@kadst43 @AmbientOSX @ajiraffe 
My hypothesis is that the reason the VO isn't helpful is that they're not listening to it, or even that it's getting cut off  when they fail the scenario - not that it isn't clear.  The important thing is to get them to realize that they should not be writing a program at this point, which I think this does.  I would do this in conjunction with two other changes:

1) Disable Blockly for this scenario (and the next one, and the similar ones in level 2)
2) Blink the whole camera selector at first, as you suggested this morning