[#303] back-porting the shapes improvements into the main 1.0.0-dev branch

broken for now, so I keep it on a separate branch, until it's working
again :P
[#303] fixed all collision issues following last commit
Allowed some of the function to be chainable
[#303] added a optional `me.Rect` parameter to the `getBounds()` function

that prevent from systematically creating a new object in function
recurrently calling `getBounds` as a local object can be created and
reused.
[#303] few fixes and improvements to shape objects
removed mentions of `collisionBox` in the documentation since this is not a valid object for event listening
Merge remote-tracking branch 'origin/1.0.0-dev-shapes' into 1.0.0-dev