[Add] ChatCore

Before merging this pull it is necessary to decide wether the versions can be considered authoritative (I took them from the Info plists of the bundles) and wether `TCMPortMapper` can use that name. `TCMPortMapper` appears to be an evolution of the original project which looks like is not being actively developed anymore. Moreover ChatCore does the right thing and imports the headers name spacing it. So if we change the name it would be necessary to set the headers dir. This is interesting because if we implement, as planned, support for headers in quirk mode there is not way for a Pod to use a fork unless setting it in quirk mode.

I'm wondering if we should consider an attribute flag like `fork_of` and that CocoaPods should use that for the installation name. We could also use the convention of `POD@FORK` and strip the suffix for installation purposes.