Update our push rules when they come down stream

Also expose a useful function from pushprocessor.

Fixes https://github.com/vector-im/vector-web/issues/1495

lib/sync.js

@@ -613,6 +613,9 @@ SyncApi.prototype._processSyncResponse = function(syncToken, data) {
         client.store.storeAccountDataEvents(events);
         events.forEach(
             function(accountDataEvent) {
+                if (accountDataEvent.getType() == 'm.push_rules') {
+                    client.pushRules = accountDataEvent.getContent();
+                }
                 client.emit("accountData", accountDataEvent);
                 return accountDataEvent;
             }