Fix $root_mail_recipient to allow arrays

According to the documentation of Mailalias, multiple
recipients should be specified as array, however, this
modules expected $root_mail_recipient to be a string.
Include dependency augeas
$mydestination should allow comma separated values

According to the example given in manifests/mta.pp,
$mydestination should allow '$myorigin, myapp.example.com'.
However, the regular expression didn't allow this value.
Merge branch 'feature/include-augeas'
Merge branch 'bug/mydestination-multiple-values'