Update to play 2.3 and bumped version to 2.3.0-RC1

There was changed nothing special:

* use `Result` instead of `SimpleResult` (which since `2.3` became a type alias for `Result`)
* use `play.twirl.api.Html` instead of `Html` (which since `2.3` became a type alias for `play.twirl.api.Htm`)

And if first case is not important, second case ruins binary compatibility.

_Note_: this pull request depends on version of `deadbolt-2-core` being `2.3.0-RC1`, though it also works fine with previous version. Please tell me if I need to rollback to `2.2.1-RC1` version of `deadbolt-2-core`. Thanks.