add map pin images
renamed and added images to constants
Merge branch 'refs/heads/3.6-dev' into 3.6-tours-annotation

Conflicts:
	Common/MITResourceConstants.h
added more image assets
Implementing drawing of annotation pin.

Implementing changing of pin color if pin is reused.
Added resources to unit tests.
Merge pull request #555 from MIT-Mobile/3.6-tours-annotation

Update map annotation images. Fixes #491