KIJIMR-47. Fold KijiMapper and KijiReducer.

KijiMapper and KijiReducer become a single interface KVOutputJob.
KijiBaseMapper becomes KijiMapper.
KijiBaseReducer becomes KijiReducer.

Signed-off-by: Robert Chu <robert@wibidata.com>
SCHEMA-109. Update to reflect API changes to KijiInstaller.