Converted ActivityViews to partial classes with common code in another file.

Also went over all of the usings in existing View files as well.
Converted OnViewModelSet method from abstract to virtual.

With the new bindings it is somewhat inconvenient to have to override that method constantly.

When a view overrides the OnViewModelSet they should start calling the base implementation as well.
This is because in the future that will probably be in charge of notifying fragments when the data
is available.