dota_prospekt - Make middle lane not so visible to other lanes

[NRacer]

Players in the middle lane are getting updates for nearly the whole map. This is causing bandwidth usage (and subsequent choppiness) to go way up. It is also unnecessarily rendering everything.

Possible areas to be improved:

• Enclose the center area (with the trashed cars) to make this less likely. This is the main culprit.
• The walkway between the two areas is also rendering often. Investigate.
• The tree area is also visible from inside the middle lane. Investigate.
• The area right next to the gates is also completely open. Don't know if I want to mess with this yet.

[NRacer]

Combined with issue #33, enclosed area resulted in 50% less bandwidth usage in middle lane and around 40% less in outside lanes. Huzza!