[READY] vehicle overmap tracking.

Addresses #3866 

The player can now track vehicles on the overmap after installing a craftable tracking device that requires a little bit of skill with electronics, the player is also required to carry a PDA in order to see the vehicles on the overmap.

The tracking device consumes 6 power from the vehicle, twice as much as a headlight, so this should make it pretty balanced.
tracking can be turned on/off through the vehicle control menu just like headlights so you can save power when you're not intending to use it.

As of now i have not noticed any bugs related to this, (except #4292), but if you would like to test this and find any bugs please report them here so i can attempt to fix them.

Here is a screenshot, click to expand.
<a href='http://s9.postimg.org/ckdki2tn3/2013_11_09_100028_1044x564_scrot.png'><img src='http://s9.postimg.org/oz0ciel57/2013_11_09_100028_1044x564_scrot.jpg' border='0' alt="screenie" /></a>