Fixes for the binding framework.

This PR fixes some things in the view bindings. Note that the changes are based on #591.

## Fixes included

* A default property binding for `FrameworkContentElement.Content` which does not exist, has been replaced by `ContentControl.Content`.
* Removed a lot of code duplication in property bindings.
* Remove a method on `ICommandBinderImplementation` which is just a special case of another method.
* Remove the out stuff in command bindings.
* Change the tests to not instantiate `CommandBinderImplementation`.
* Give `SetValueToPropertyChain` a Try prefix like the other methods.
* Make the code of command bindings more similar to the code of property bindings.