Revised work on OpenSearch autoconfiguration

Thanks to Matt Ramey (mrmateo) for the suggestions
Extend Atom transformer to provide Media extension format thumbnail and content.

This improves support for Windows Federated Search. It adds a dependency on the Abdera media extension - seems mature enough.
Fix help text for Catalog search.
Fix additional typo identified by Phil Klinefelter

See https://github.com/codice/ddf/pull/15#commitcomment-3640160
DDF-98: Fixes to SourcePoller / SourcePollerRunnable to status sources in a thread
DDF-99: Updated DDF to build on Karaf 2.3.2.

Had to update code to utilize new xerces 2.11.0 lib in endorsed and removed patched webconsole.
DDF-99: Had to add new spring bundle repo for karaf dependencies.
DDF-98: fixed formatting and added locks in the SourcePollerRunnable to prevent multiple status threads running concurrently on the same source
DDF-99: Updated spring repo references to point to the correct URLs.
DDF-98: incorporated code review comments
DDF-99: re-added karaf 2.3.2 upgrade changes after bad merge
DDF-102: Adding checking of content-disposition.

Added check for filename in HTTP header and also converted code to use SLF4J.
DDF-94 null check for metadata field of metacards.
DDF-94 Added unit tests for how predicates handle null contextual data.  Added null checks into Contextual and Entry Predicates.
DDF-94 removed other potential NPE identified in code review.
DDF-94 additional unit tests for null operation.
DDF-93: added check to prevent adding sample update less than one second interval
DDF-92 Solr Catalog Provider getContentTypes returns content types whether or not they contain versions.
DDF-92 fixed code review comments
DDF-102: Making some fixes from code-review.

Removed some duplicate calls and updated some logging.