Merge pull request #9672 from ferjm/bug861921.lowdevicestorage.aux

Bug 861921 - Notify the user about the low free storage situation. r=eti...(cherry picked from commit fad3da3881351a6a2b66fcddb2fe2dd0b72eddb2)

Conflicts:

	apps/system/index.html
	apps/system/locales/system.en-US.properties