Added "rollback" snapshot type to schema.

foris_controller_modules/schnapps/schema/schnapps.json

 {
     "definitions": {
         "number": {"type": "integer", "minimum": 1},
-        "type": {"enum": ["pre", "post", "type", "single", "rollback"]},
+        "type": {"enum": ["pre", "post", "time", "single", "rollback"]},
         "snapshot": {
             "type": "object",
             "properties": {