Store 'global' objects in the Core object.

This way it is possible to do require('Base/Core').Class. Because of that it would be much easier to 'install' those on the global object, in some specific builds.

I also added a `Core.install` method, which can copy those objects and functions on window or other objects.

I probably would just use a AMD loader, but for people who prefer those stuff to be on the global object, like it always used to be, can do that now.