Look for imported Yorba bugs and clean up the first comment if found.

When Yorba moved their application hosting over to GNOME's
infrastructure for Geary, Shotwell, and other projects, the bug
import from their bug tracker produced buzilla bugs containing the
complete bug history in comment 0.

This looks for such import bugs, cleans up the text a bit to to make
it somewhat more readable, and replaces `#1`, `#2`, etc in the text
with `Comment 1`, `Comment 2`, etc so early gitlab issues don't get
spammed with huge numbers of mentions.