Add priority option for daily snatches (inc force)

This adds a priority option that allows the user to specify the
priority to be used for daily/recent snatches instead of the default
high value ‘100’.

This also includes the use of priority ‘force’ which will let nzbget
download the task even if the queue is paused.
Merge pull request #713 from piejanssens/dev

Add priority option for daily snatches (inc force)