Add missing isolates column to manage.py --remaining.

This permits to quickly determine the low hanging fruits, that is, the ones with
an .isolate file already.

Add check when converting a test that at least a .isolate exists for it.
Print out all the builders converted with --convert.

Add builders not supported on Swarming to the blacklist, to remove the need to
edit the json files manually.

R=phajdan.jr@chromium.org
BUG=98637

Review URL: https://codereview.chromium.org/1050103002

Cr-Commit-Position: refs/heads/master@{#323482}
1 file changed