Explicitly set enconding for javac for sbt CLI

Otherwise the system default will be used which might cause hickups.

build.sbt

@@ -11,6 +11,8 @@ val gsonVersion = "2.8.5"
 val modelmanagementprovider = ProjectRef(uri("https://git-st.inf.tu-dresden.de/cwerner/role_model_management_provider.git#master"), "modelmanagementprovider")
 val uiProvider = ProjectRef(uri("https://git-st.inf.tu-dresden.de/cwerner/role_ui_provider.git"), "uiprovider")
 
+javacOptions ++= Seq("-encoding", "UTF-8")
+
 lazy val generator = (project in file("."))
   .settings(
     name := "CodeGenerator",