drop 'nightly', handle fedfind 2 and pungi 4 nightlies
First steps in adapting relval to fedfind 2 and Pungi 4. We
drop the 'nightly' subcommand entirely because all that woo
is gonna move into a new dedicated fedmsg consumer for creating
events when new composes appear. So now we just use 'compose'
for creating nightly events as well, when/if we ever need to
do it manually.
We also allow creating events by passing a Pungi compose URL
rather than release/milestone/compose, using the wikitcms
get_validation_event_url code.
size_check gets adapted to fedfind 2.x, the conversion wasn't
too painful happily enough.