[CLOSED PR] Merge Engineer and Mechanic access

[UmbraDrake]

I feel like I can see the both pros and cons to this, but I have a couple of issues;

1) I can see mechanics raiding engineering stockpiles more often than they already do (I mean, even if they don't get access, they just break in regardless).

2) Engineers getting into mechanics makes more sense, especially with the ruck kit, but I can imagine engineers getting bored and doing mechanics stuff instead of paying attention to the engine and letting it die by omission/using mechanical wizardy to break it even further (if that's even possible)