Editor

@kadst43 @eric79 

Changes:
- Modified grid.js to allow rover placement in editor without map loaded
- Modified rover.js to remove implied knowledge of other nodes in the scene
  - Moved scenario changed listener to scene.js
- Added rovers to editor
- Modified isAtPosition to take a 2 element array rather than 2 individual numbers
- Cleaned up action and boolean function scripts
- Modified editor styles
- Added trigger dialog
  - Independently handle all conditions and actions
  - Independently handle most argument types
- Build trigger JSON from dialog
- Save triggers to scenario
- Load scenarios from file