SCHEMA-83. Updated RELEASE_NOTES.txt.
SCHEMA-82. Add table location to KijiCell.

DecodedCell replaces KijiCell as unit of cell data and writer schema.
KijiCell wraps a DecodedCell and adds family, qualifier, timestamp.
KijiCounter no longer exists and is KijiCell<Long> instead.

Signed-off-by: Christophe Taton <taton@wibidata.com>
SCHEMA-143. Hide KijiURI constructor behind KijiURIBuilder.