nfsdcld: add routines for a sqlite backend database

nfsdcld: add routines for a sqlite backend database

Rather than roll our own "storage engine", use sqlite instead. It fits
the bill nicely as it does:

- durable on-disk storage
- the ability to constrain record uniqueness
- a facility for collating and searching the host records

...it does add a build dependency to nfs-utils, but almost all modern
distros provide those packages.

The current incarnation of this code dynamically links against a
provided sqlite library, but we could also consider including their
single-file "amalgamation" to reduce dependencies (though with all
the caveats that that entails).

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>