Added optional FilterArea to displayObject (for optimisation)

Reverted interaction manager (for now) as not working as expected (no
bubbling)
Added removeChildAt method

the ability to remove a child in a specific index.
updated removeChildAt, removeChild, removeChildren
updated removeChildAt and removeChild. removeChildren has now a begin and end value.
removed spaces
Merge pull request #656 from andrevenancio/dev

added removeChildAt, added removeChildren
Fix logic error in DOC
Manually merge #657
Fixed anchor point bug in canvas

tilingSprites anchor was not being respected in the canvas renderer