Add includes parameter that takes string

[realityforge]

Currently the includes parameter on @Injector and @Fragment takes java types. It would be useful to have another includes style parameter that takes a string that indicates the name of a class. This would allow the inclusion of package access components in the fragment or the injector without creating synthetic @Fragment to represent the type or changing the access level to public for type.

[realityforge]

While this initially seemed appealing because it meant we could have a central fragment or injector that collected package-access dependencies. In practice, it seems it is less complex to define a fragment per-package where we want to expose package access components.