remove filteReddit.options.notification

and to heck with migrating the option into notificationTypes
only show filteReddit "posts filtered' notification if min % (posts/page) filtered per filteReddit.options.notificationThreshold
Merge pull request #1826 from andytuba/filtereddit-notificationthreshold

Only show filteReddit's "posts filtered" notification if a minimum % of posts are hidden