Added a new gravity generator which will produce gravity for the station.
Sprites by Ausop, which he posted in his sprite thread.

The gravity generator is very sturdy, as it is almost indestructible, but explosions can break it and it will need repairs.
Changed C4 to stop del()'ing and instead will only use ex_act().
Added an interact_offline variable for machines that will allow you to interact with them even if they are depowered. The gravity generator only uses this at the moment.

Removed the stun that people get when gravity changes.
Shuttles have gravity still.

Added a gravity generator room to the west of Engineering. It is very secure, with a foyer and requiring CE or Captain access. There are instructions on the table for repairing and enabling/disabling the machine.
* Gave the supply area gravity.
* Removed a misplaced object on the map.
Typo fixes. I'm keeping the comma-less but.
Shuttles changing location will update the area's has_gravity.
Added a SMES to the gravity generator room, unhooked the room from the main station powernet.
Merge pull request #3086 from Giacom/gravity_generator

[MAP] Added a new gravity generator which will produce gravity for the station.