Implement shift+leftclick for fast object pickup

[donnierussellii]

Shift+leftclicking a container/body once shows contents, leaving mouselook alone. Second time puts important object on cursor then in inventory if possible, also leaving mouselook alone.

Shift+leftclicking an object like a patch or weapon puts it on cursor then in inventory if possible, leaving mouselook alone. Any weapon added this way (to an empty slot) is selected.

Shift+leftclicking something like a keypad turns mouselook off.

[Interrupt]

Looks like the Travis-CI builds were failing for some reason here, not sure if that's related to this change or if it was just bad timing. Edit: Related to https://github.com/Interrupt/systemshock/issues/243