update to play 2.3

missing scala 2.11
compile with scala 2.11 as well

sbt must be started with -Dplay2-war.sbt.scala.version=2.11.1
to use scala 2.11.1
Merge branch 'feature-#247-be-compatible-with-play-2.3' into develop

Conflicts:
	project-code/plugin/src/main/scala/com/github/play2war/plugin/Play2WarCommands.scala
	sample/project/Build.scala