Cron daemon, which was triggered by WordPress method, was deactivated
by deletion from DB and it caused the lost of all log data about it.
This commit changes the implementation so that the daemon is deactivated by changing status flag.
[MAILPOET-1457]
* Abstract key state to unbound it from the API response codes
* Rename SendingServiceKeyCheck task for clarity
* Add a setter for the API key in the Bridge API class
* Make some smaller fixes