pmdads389: 389 Directory Server PMDA

This is a 389 Directory Server PMDA, ds389, tested on RHEL 6
(389-ds-base-1.2.11) / Fedora 20 (389-ds-base-1.3.2). It provides server
and database (userRoot) metrics and chaining database could be easily
added if deemed useful. Access log statistics provided by logconv.pl
would be something to consider for a separate PMDA, i.e., they are out
of scope for this PMDA.

RHDS Administration Guide sections 15.6-15.9 document all the above,
the statistics described in 15.7 and 15.8 are being collected:

https://access.redhat.com/documentation/en-US/Red_Hat_Directory_Server/9.0/html/Administration_Guide/

The only real concern I have at the moment is the need for the
query_interval/timestamp stuff which is pretty ugly but when doing
e.g. "pminfo -dfmtT ds389.userroot" two successive queries are done for
some reason, I think we should avoid such needless LDAP queries.

Connection options could be perhaps improved but using the PMDA on other
than localhost doesn't sound like a critical feature.

To test this locally, install the 389-ds-base RPM and run setup-ds.pl and
you'll have 389 DS up and running.