Add cookie support to HttpRequest and add support for callbacks on CC.ControlButton

I'm not very familiar with git, so I apologize for lumping two changes into one pull request.

Two things are included in this request:

1. The changes to HttpClient.cpp adds support for cookies. They're stored in a hardcoded location, but I don't think this is an issue since cookies should "just work", and this change makes that happen. As an example, you can see how cookies are handled in iOS' code, where the user of the SDK never needs to specify or know where the cookies are stored; it's enough to simply know that they are being stored. Clients of HTTP libraries expect cookies to be received and stored by default, and this functionality is key in maintaining sessions in many apps such as games that use HTTP as a transport for server synchronization.

2. A manual binding is added for CC.ControlButton so a client can add their own callbacks to CC.ControlButton. Additionally, the event enum is imported into JS as well. I don't know if there's a better way to do this than maintaining it by hand, but looking at the existing code base it appears that this is the way it's been done so far.