Feature: Update ECS branch with lastest changes in master (as of a951126c)

Synchronize the ECS_Updates branch by merging the latest commits from master branch into ECS_updates.

Changes included from master:

$ git shortlog 010e1cc1...a951126c --no-merges
Aaron Bray (1):
BUG: Add missing file to CMake

Harald Scheirich (7):
BUG: swap members if necessary
ENH: Show average physics frame times in stats
ENH: Add unit test for closest point on segment
BUG: Add test and fix calculation bug
ENH: expose distance constraint
ENH: Expose ConstraintContainer and support
FIX: Order agnostic constructor was not working correctly removing it

Jacob Moore (3):
BUG: Debugging collision
ENH: Fixing ct wall constraints
BIG: Fix collision order