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 
I'm not sure it should tell them two over and one up for two reasons: 1) at this point, they should have figured that out, and 2) even if they didn't, we'd be giving them the answer.