Add mercurial evolve package, make it a dependency of hgsrht

hg.sr.ht: normalize init scripts

Add hg.sr.ht-webhooks service

Add core.sr.ht migrations to hg.sr.ht post-upgrade

Make local redis service optional

Add extra gunicorn args to *.init

Update hg.sr.ht.post-install

Add hg.sr.ht package