incoming: remove linkstart and linkend until things are actually ready

tests: test read_linter_config() from checker.py

tests: test run() from checker.py

incoming: save linkstart and linkend for lines (not used yet)

viewer: make task blocks collapsible (except cleanup)

incoming: use a subquery for Check.ordinal instead of a separate query

models: drop Check.raw field (not worth storing in the same table) Replaying checks can be done (and is easier) when storing checker output in plain files, so let's lighten up the load on the database.

incoming: strip linebreaks from lines before storing them

incoming: mark "job failed" line as a failure

tests: test another regex in incoming (luacheck-style linter output)