CCAction/ActionManager bugfix

here's an initial bugfix with a test for issue 945 as spoken about here:
http://www.cocos2d-iphone.org/forum/topic/22955
There's not much to it, but I'd love to hear feedback before I clean it up/make sure all actions work with it properly etc.
There's a new target SequenceTest in the mac project that demonstrates adding and stopping several
sequence/repeat actions independently on a single node.
Lemme know what you think!
-j