B-48882 - Archiving: Hadoop Adapter for Retrieval of Archived Events

NOTE:  there is a corresponding pull request on atom-hopper-setup (same branch name) which is required by this pull request, and requires it as well.

To support archive adapters I added the following:

-	Expanded FeedSource interface to declare the “current” link URL for archived feeds.
-	Expanded FeedSource interface to declare the “next-archive” link URL for feeds which have archived feeds.
-	Added AdapterHelper class to handle archive-related logic for adapters.
-	Expanded atom-server.cfg.xml format to allow archive-feed & current-feed which are used to declare links between current feeds & archived feeds.
-	Updated regression paging.jmx regression test to verify interface between current feeds & archived feeds as well as verifying the archived feeds prev-archive & next-archive links.