Added Public Works spawning...

A fairly rare building, currently only 1-3 will spawn in a map but it may make more sense to balance it to 1-2.  It should be a nice surprise to find it.   

I'm not sure why but I can't get it to spawn without the mfb(OMS_FLAG_CLASSIC)... I'm not sure how many people will be offended by this since the FEMA camp also has it.