[Tilesathome] New client error feedback API

[spaetz]

I just implemented the server-side and committed a new URL to the t at h client. In case of putting a job back to the server, the client will now call some URL like this:

http://tah.openstreetmap.org/Request/feedback/?x=1042&y=1845&min_z=12

This will reset all active (in rendering) requests back to unhandled, which will imply that your number of active requests will shrink on an error.

I did this without any client authentication for now, to keep changes minimal, however, I plan to make the t at h client authenticate at this page, then the server will be able to only reset a request if the corresponding client is jsut rendering it.

Hope that helps,
spaetz