Bug 864751 - Add profile directory define

Conflicts:
	Makefile
	build/settings.py
Catchup makefile from master
Bug 848604 - used apps.list to pick apps from apps/*, external-apps/* & GAIA_DISTRIBUTION_DIR

Conflicts:
	.gitignore
Bug 879563 - Added option for installing external addons. r=ochameau

Conflicts:
	Makefile