Adds NotifyPropertyChanged wrapper.
Update IReactiveNotifyPropertyChanged with the new interfaces.
Update IReactiveObject with the new interfaces.
Update Android classes.
Update Cocoa interfaces.
Update IReactiveNotifyCollectionItemChanged.
Fix style.
Update IROObservableForProperty to translate to ObservedChange.
ReactiveList also understands the new stuff.
Even ReactiveObject uses the new interfaces.
What is this stuff even doing here.
Fix invalid cast.
Merge branch 'binding-fixes' into indexer-bindings
Fix tests.
Add an ExpressionRewriter.

This expression rewriter allows us to support index, arraylength and
arrayindex expressions.
Add static  ExpressionRewriter.
Rewrite expression before usage.
Support convert operations.
Add failing tests for indexers.
For indexers we need the parameters which are available in the expression.