Various Google Maps definition fixes

- Added draggable to various overlay objects
- Added StrokePosition to PolygonOptions, CircleOptions and
RectangleOptions.
- Fixed MVCArray return and argument types for overlay objects' path
methods.
- Fixed DrawingManagerOptions and DrawingControlOptions interfaces, made
all properties optional.
- Made GeocoderRequest.address optional, it's not required when using a
LatLng for geocoding.
- Fixed SteetViewPov.pitch typo.
- Added addListener to MVCObject
Merge pull request #501 from qcz/smallfixes2

Various Google Maps definition fixes