Removed dependency on Bullet.
Added prototype code for thing resting contacts.
Renaming source files to match new convention.
Renamed identifiers to match new naming convention
Added prototype iterative LCP solver.
Updated math lib. Added prototype thing collision
Fixed errors on Clang trunk and Intel graphics.
Refactored some physics queries out of presenter. Removed point_inside_sector and segment_adjoin_path level queries from the level presenter.
Refactored model hierarchy visiting in level view. Added generic model/animation visitor interface to key presenter. Updated prototype collision code and level view to use the generic interface.
Fixed z-buffer initialization with SFML 2.1
Bounded physics step by movesize template param.
Added thing collision message dispatch.
Updated pool object with new semantics.
Fixed crash-on-exit bug involving surface anims.  Replaced recorded surface animation and thing foley sound channel IDs with option pointers.
Refactored physics code into physics presenter.
Added path thing blocking.
Fixed key and sound presenter bugs.               Fixed lockup bug in key presenter. Fixed attenuation bug immediately after sound playback start.
Refined sphere types, added ss-plane helper.
Fixed temp bryar angle, fixed stopsurfaceanim bug.
Added rate-limiting contacts.