Highlight seeding torrents in case of any problems with trackers

The idea is to highlight completed torrents that have no chance to
continue seeding (all trackers are disabled or have error state
and none of which are timeouts) with red. Highlight torrents which
seeding may continue automatically soon (all trackers are with
error or warning state but some errors are timeouts) with some
greenish. And to highlight torrents that supposed to be seeding
but still have some warnings (all tracker states contain warning
messages) with some yellowish.
In case at least one tracker reports OK state with no warning - it
will be left green as default.

Requires following functionality in libktorrent:
https://phabricator.kde.org/D25136

Differential Revision: https://phabricator.kde.org/D25137