Allow a mode of operation without HS connection (#601)
* Allow a mode of operation without HS connection
Instead of blocking the first sync on getting the push rules and
filter, load sync data from disc.
When the client comes online, the push rules will be acquired and
a sync cycle started. This could be immediate if the client is
already online.
This could be a breaking change for clients that get push rules
before a successful sync has been done.
