Show "empty" when a menu is empty

FIX #188 : "empty" text
FIX possible multiple response where it was not allowed
Merge branch 'master' of github.com:Heigvd/Wegas

# By Benjamin Gerber
# Via Benjamin Gerber
* 'master' of github.com:Heigvd/Wegas:
  JS - Descending order for inbox and crimesim results
  treeble now using existant events
  Remove timer on inbox
  Close #184
Revert "Remove timer on inbox"

This reverts commit 25bbae565fc3175586497193c1dfdf1006f79881.
Merge branch 'master' of github.com:Heigvd/Wegas

* 'master' of github.com:Heigvd/Wegas:
  Fix choicedescriptor duplication
  Added game scope

Conflicts:
	wegas-core/src/main/java/com/wegas/core/persistence/variable/primitive/NumberDescriptor.java
Merge fix