New vehicle part (Welding Rig) and RV kitchen bugfix

This adds a new vehicle part, the welding rig.  Similar to an RV
kitchen's hotplate, this allows you perform tasks that require a welder
or a soldering iron by drawing power from your vehicle's storage
battery.  The recipe for this is similar to RV kitchen, but requires as
components a soldering iron, some wire and either 1 regular welder or 3
makeshift welders.  It can also (rarely) spawn in a garage.
I also wanted you to be able to examine this when it's installed and use
it like a soldering iron (repair plastic/metal/kevlar and cauterize
wounds), but couldn't figure out how to make it work.  If anyone has any
idea how to do this, please let me know!

Tested and works

PS - While making this, I also found and fixed a typo in the RV kitchen
recipe, and added it to the garage spawn list.  If this should be
separate, tell me and I'll move it.

EDIT - I think I did it! No more bogus merge things! Yay!  Sorry about that, apparently the "sync" button in Github client is evil and not to be trusted.