Use psql instead of pg_restore to restore SQL dump file.

These fixes will allow a restore of gitlab when the backups and
repositories directories are in non-standard locations (ie sub-dirs
of gitlabhq).  Also allows the restore to be run from script
overriding the need of a user to confirm the rebuild of the
authorized_keys file.

By default there is no public/uploads directory when no attachments
are uploaded. Prompt users to create the uploads directory during
install otherwise the backup task will fail.

Place mysqldump args in single quotes to avoid error if password
contains special characters.

Signed-off-by: Axilleas Pipinellis <axilleas@archlinux.gr>