[Content] Support for update methods and editable attributes

The content api has editableAttributes array which lists the attributes that can be updated via update method.

Editable attributes are non-readonly attributes in the spec (name, description, orientation, geolocation, rating)

Geolocation requires tizen.SimpleCoordinates() which is added to the Tizen API.

Also some typo fixes.

TCT pass rate: +12% (62->74)

BUG=XWALK1989

Note: updateBatch method is still not done so the above bug is only partially fixed. 
I'd prefer define `STR_ID`, `STR_NAME` and `STR_DESCRIPTION` in `ContentInstance::HandleUpdateRequest()`, as they are only used in that function.