Config option needed for Flapjack major version, and change Redis write behaviour based on that

[Ali Graham]

Flapjack v2 requires a write (containing any data) to the events_actions list once new data has been placed on the events queue, for safely interruptible event processing. flapjackfeeder will need to know whether or not to place that data there, and then do it if so.

(That queue name is actually configurable, and then suffixed with "_actions", I'll see if I can make that configurable via the config line as well.)

[Ali Graham]

Fixed in #17