tracker_status improvements (inc translate status in client not core)

[Cas]

tracker_status is currently the only translated value in torrentmanager.py which causes issues with filtering for keywords such as "Error", although a workaround for this issues has been applied already: ​9a1ae06033b

For reference the current format in torrent.py set_tracker_status is:

"tracker_host: tracker_status: tracker_message"

It might be more useful to pack this as a dict and let the clients sort out translation and display.

Further to this the ​tracker_error_alert has a few more details that just the message:

The times_in_row member says how many times in a row this tracker has failed. status_code is the code returned from the HTTP server.

Finally only one tracker's status can be stored but adding a new trackers_status key more detail could be held and would be useful for implementing #1015

[Cas]

Milestone renamed