Add a Collision Mesh Editor like the one in Torque2D

[jwu]

A collision mesh editor to help user edit convex shape collision mesh.

Request source:

• http://forum.unity3d.com/threads/101811-ex2D-the-best-2D-sprite-solution-for-Unity-RELEASED?p=685024&viewfull=1#post685024
• http://forum.unity3d.com/threads/101811-ex2D-the-best-2D-sprite-solution-for-Unity-RELEASED?p=685734&viewfull=1#post685734
• http://forum.unity3d.com/threads/101811-ex2D-the-best-2D-sprite-solution-for-Unity-RELEASED?p=689280&viewfull=1#post689280