Rename the platform into Web Platform

[hamzaed]

I think this platform should be called WebPlatform instead of ReactPlatform. Indeed, React is the technology used to implement the chat widget but still I think we should use a general form to describe the platform (it provides a Web widget to communicate with Xatkit background).

[gdaniel]

Agreed, already discussed with @jcabot and we came to the same conclusion (and same name!)