Distant Statics in the form of Object Paging

Add support for showing distant statics.

Considerations:

• Support removing/disabling meshes on the fly?
• Do we need to cache anything to disk?
• "Forum post":http://forum.openmw.org/viewtopic.php?f=6&t=4621

(RM-2386 from redmine: created on 2015-02-18 by scrawl ., )