kiji-express: EXP-136. Implement a trainer for linear regression models.

issue: https://jira.kiji.org/browse/EXP-136
review: https://review.kiji.org/r/1125
commit: https://github.com/kijiproject/kiji-express/commit/e4d1bd6ee587ca44da692359aa5433cc7a11fae2
kiji-schema: SCHEMA-553. HBaseKijiRowData.getReaderSchema() isn't compatible with layout 1.3

 - Deprecate KijiTableLayout.getCellStorage(KijiColumnName)
 - Deprecate KijiTableLayout.getSchema(KijiColumnName)
 - The prefered way becomes to use KijiTableLayout.getCellSpec(KijiColumName).
 - Improve CellSpec javadoc.
 - AvroSchemaResolver becomes an interface, SchemaTableAvroResolver implements it.
 - Lots of fixes in CellSpec wrt. to the new AVRO type.
 - Proper CellSpec initialization with layout-1.3.

issue: https://jira.kiji.org/browse/SCHEMA-553
review: https://review.kiji.org/r/1140
commit: https://github.com/kijiproject/kiji-schema/commit/978373326c7084d1261fe7c1dffa558a59a025a1
kiji-hive-adapter: KIJIHIVE-39. Force user classes to take precedence for MapReduce jobs created within Hive.

Signed-off-by: Daisy Zhou <daisy@wibidata.com>
commit: https://github.com/kijiproject/kiji-hive-adapter/commit/2d5abab930ebaf8311134b3f88c5e36432b3268e
kiji-model-repository: KIJIREPO-29. Tool to toggle the production_ready flag for an existing model lifecycle.

issue: https://jira.kiji.org/browse/KIJIREPO-29
review: https://review.kiji.org/r/1131
commit: https://github.com/kijiproject/kiji-model-repository/commit/0adfc4e8ccc236721826f02902f97797784f9884