Support device group definitions from v2 (#4591)

* Support device group definitions from v2
Disable editing v2 groups.

V2 Device groups are defined as follows:
pattern = WHERE query with ? placeholders for values
params = json encoded array of values

* Can't array_unshift something that isn't an array...

sql-schema/139.sql

@@ -0,0 +1 @@
+ALTER TABLE `device_groups` ADD `params` TEXT NULL DEFAULT NULL AFTER `pattern`;