Toggle armor visibility, toggle cargo part highlighting

Some options people have requested:

* The armor visibility (that is, armor's color being used instead of the displayed part's color) can now be toggled on/off in the options.
* The part highlighting (where cargo parts with items have inverted colors) can now be toggled on/off in the options.
* A message is printed when walking over a vehicle part with items, so you don't have to 'e'xamine every vehicle part to loot cars even if you have highlighting off.

Both options are in the Interface section and default to true. Neither option requires a restart to take effect.