INSTALL: Added description how to create additional dove* user/group.
`doveauth' user and group for the authentication process and the group
`dovemail' for mail related Dovecot processes.
# use glob syntax.syntax:glob*~*.py?.*.swp.swpdoc/buildbuilddebian/vmmdebian/*.logdebian/*.debhelperdebian/filesdebian/*substvars.pc*.egg-info