Signing Service initial support (bugs 1070189, 1070191, 1070227)

Bug 1070189: Call the trunion API (not tested with servers yet)
Bug 1070191: Signing management command
Bug 1070227: Script to sign all existing add-ons
ah, I see `tempname` is also used line 53, I missed that. Forget my suggestion, your solution is better ;)