Platform conflicts with Platform in XF -> Rename to something else

[jamesmontemagno]

See: #264

We should rename to something else. CurrentPlatform perhaps?

We use this currently for ui thread updates and detection.

[mattleibow]

CurrentPlatform diverges a bit form the other APIs with a more "noun-based" naming method. Any ideas of better names?

[jamesmontemagno]

Yeah, I think something else for V1 would be needed. Not sure what though.

[migueldeicaza]

Good call, given the current API surface of what is in Platform, this has very little to do with the paltform itself.

This really should be called MainLoop. Let us do that.

[Redth]

Platform isn't just used for UI thready things currently, so I think if we name those API's to MainLoop we still need to come up with another name for things like Android's Platform.Init(..) and Platform. OnRequestPermissionsResult(..).