Since we do not use neomutt anymore. Additionally, perhaps a 'mail-'
prefixed system is better for scripts etc which run independent of a
specific MUA.
Renamed `mutt2task` to `neomutt-2task`, and renamed `sync-mail` to
`neomutt-syncmail`.
Changed key maps accordingly. Also systemd service even though I don't
think I'll use it again.
Since I am striving for closer connection between my task management, my
mail suite and my calendar appointments, it makes sense to unify all
'office' tasks into the single office module instead of keeping
taskwarrior outside of it.
