Rudder

The first reason is that scala 2.11 is EOL, so as for Java 8, better to switch now toward a solution that will be supported for some time.

The second reason is that it leads to 25% (25Mo) decrease in war size (75Mo vs 96Mo - still huge, but better).

(there is also a little better compilation time, not very significative, and I have just a couple of data point looking like:
Scala 2.11: mvn -Dmaven.test.skip=true clean install 591,72s user 7,99s system 340% cpu 2:55,92 total
Scala 2.12: mvn -Dmaven.test.skip=true clean install 568,38s user 4,80s system 349% cpu 2:43,78 total
)

The last reason is that the migration is relatively easy. Three points to notice:

- scala-actor is gone (see #10119)
- lift "bind" is gone (so use CSS selectors)
- lift-json JField aren't JValue anymore (so use json match { case JObject(JField(...)) } in place of json match { case JField(...) } )