New map feature: SAI's

Most places have some form of telecommunications cabinet in their neighborhoods. I decided it would be a nice addition to the cities in-game. The only SAIs I ever really have seen are usually behind a chain-link fence, and are grouped. Most of the time the ones I have personally seen contain some type of telecommunication equipment, along with the much larger DSLAM cabinet that has something to do with DSL internet.

For those who have no clue what any of this is, I am talking about these things:
![](http://www.skullbox.net/dslam.jpg)

The frequency may still need to be tweaked a bit, but after playtesting it myself they seem to be appearing alright.