Some (embedded) systems don't provide getent(1). The workaround parses
/etc/passwd and /etc/group under the assumption that these sysems only use local
users and groups.
- add support for authorized_keys options see sshd(8)
- add support for explicit comment after key
- do not allow a key to exist more then once in an authorized_keys file
- remove all conflicting keys
Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>