Update local aports location in 'init'
This addresses #246 (closed) by updating the local aports folder location every
time pmbootstrap init
is called. This location would change if an
existing config file is in ~/.config and pmbootstrap's location has
changed (e.g. when switching to a different fork in a different location
on disk). With this commit, you just have to run pmbootstrap init
and
change (or accept) the existing config values and aports location is
updated automatically.