Some (embedded) systems (and Mac OS X) don't provide getent(1). The workaround
parses /etc/group under the assumption that the system only uses local users and
groups.
- add new --state parameter and support for deleting groups
- add new --system parameter to create system groups if supported by the
os
- remove special case for legacy redhat/centos versions, they are long
gone
Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>