SCHEMA-310. Ensure pooled tables are released when marked idle.

When the idle connection cleanup thread releases pooled table objects, it was
originally releasing the underlying HBase table instead of the decorated pooled
table which breaks encapsulation.

Reviewed by: taton
SCHEMA-311. Renamed Connection to PooledKijiTable.

Renamed the internal Connection class to PooledKijiTable. This better represents
the decorating of a KijiTable for pooling purposes.

Reviewed by: taton
SCHEMA-303. KijiRowFilter should have a proper serialization/deserialization

 - Row filters are now serialized to/from JSON.

issue: https://jira.kiji.org/browse/SCHEMA-303
review: https://review.kiji.org/r/128/
SCHEMA-282. KijiPager does not take into account ".withMaxVersions()" set in the KijiDataRequestBuilder

 - KijiPager implementation split in two versions: HBaseKijiGroupPager and HBaseKijiMapPager.
 - Update KijiPager documentation to reflect actual behavior and limitations.
 - Map-type pager now filters cells
 - Fix checkstyle to allow empty block statements with a column (eg. else { /* Blah */ }).
 - Debug.toString() to pretty-print HBase filters.
 - Implement toString() for various Kiji classes.
 - Update paging-test layout to use RKF2.
 - unit-test and integration-test for the pager.

issue: https://jira.kiji.org/browse/SCHEMA-282
review: https://review.kiji.org/r/108/