WIP: (Mostly) working polling directive

Example implementation on city/region upload page

This is here to get some initial feedback on implementation, thoughts on ways to improve before I finish this up and implement it on the other pages tomorrow. Please comment!
I'm not sure this should be a pollingError; that sounds to me like there was a problem with the polling itself and the poller (?) wasn't able to get any date, but that's not what's happening here.