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 
```
- setObjective:
 - ""
```
Will clear the text and it's not ambiguously explicit. If you still agree, I'll make no param clear the text.