Fix for types - isString and isNumber.
Modified several tests to pass on VS Emulator for Android.
Fix page background to be applied in onLoaded method.
Enhancements for dependency-observable - it is now possible to add defaultValueGetter function to extract default value for a property. It can also be cached or not.
Remove android_constants because they are per theme and we cannot use them safely.
Fix for SearchBar reseColorProperty method.
