Split DB tests and add code to retrieve only thread parents
Set parentOnly flag based on input
Add support for "parent-only" in <recent-items/>
Merge pull request #165 from surevine/recent-items-parents

Recent items parents
Fixes federated requests for NodeThreadsGet.
NodeThreadsGet: Adding remote-server-discover attribute for remote
requests.
Tidy up code
Fix memory issues (again - not sure where last attempt went)
Merge pull request #166 from surevine/threads-get

Threads get
Added JSPF plugin framework as a dependency
Refactored payload validator code to be less Atom specific

This is in preparation for future support for different payloads.
Made content validation more generic and added validator for IODEF

Removed Atom knowledge from publish processor by:
- Passing generic item element into AtomEntry rather than (Atom specific) entry element
- Pushed local and global ID generation, and in-reply-to getter, into validator