[schema][experiment] Allow - in database name

All other assets can have it. There seems to not be
any reason to make database an exception.

beat/core/schema/experiment/common.json

@@ -74,7 +74,7 @@
 
     "versioned_database": {
       "type": "string",
-      "pattern": "^[a-zA-Z_][a-zA-Z0-9_]*/[0-9]+$"
+      "pattern": "^[a-zA-Z_][a-zA-Z0-9_-]+[a-zA-Z0-9]+/[0-9]+$"
     },
 
     "dataset": {