Work on EXP-160: Refactor extractors.

Refactor extractors so they can be configured on appropriate lifecycle phases.
EXP-168. Normalize naming of Avro Classes.

The names of Avro records for columns and filters have been changed from
'*Spec' style to 'Avro*' to match other classes and distinguish
from records like 'AvroInputSpec' (which legitimately should end in 'Spec').

issue: https://jira.kiji.org/browse/EXP-168
review: https://review.kiji.org/r/975
Update dependencies for release.
Updated RELEASE_NOTES.txt for release.
[maven-release-plugin] prepare release kiji-express-0.8.0
[maven-release-plugin] prepare for next development iteration
EXP-186. Update Scalding version used by KijiExpress.

issue: https://jira.kiji.org/browse/EXP-186
review: https://review.kiji.org/r/984
Update RELEASE_NOTES.txt for release.
[maven-release-plugin] prepare release kiji-express-0.8.1
[maven-release-plugin] prepare for next development iteration
EXP-172. Allow users to read SpecificRecords in KijiExpress

issue: https://jira.kiji.org/browse/EXP-172
review: https://review.kiji.org/r/987
POM-9. Upgrade to Avro 1.7.5

issue: https://jira.kiji.org/browse/POM-9
review: https://review.kiji.org/r/1002
EXP-189. Add a cleanup method to the score producer.

There are tables and resources that are opened during the setup of the producer
but not closed hence throwing exceptions in the finalizer if the producer is in
a long running process. This adds a cleanup method to close and release
resources.

Reviewer: robert
EXP-130. Implement an API for running valid subsets of model lifecycle phases.

review: https://review.kiji.org/r/1022
issue: https://jira.kiji.org/EXP-130
Contrived iterative prepare job.

Reviewed by: robert
EXP-173. Users need to be able to page through columns with many versions.
Users of express may now request that column paging be enabled. If paging
is enabled, a PagedKijiSlice is returned in the associated tuple field. A
PagedKijiSlice allows users to iterate over all cells in a column, while
limiting the number of cells in memory.

Reviewed By: Robert Chu
EXP-192. Ensure that phase classes can be properly loaded.

This will ensure that phase classes can be loaded from the right classloaders
instead of just restricting to the class loader of the code executing the
Class.forName method call.

Reviewer: robertchu
EXP-178. Get rid of all Avro unions in ModelDef and ModelEnv

issue: https://jira.kiji.org/browse/EXP-178
review: https://review.kiji.org/r/1021
Fixes regression test hanging

by increasing permgen space for the scalatest jvm

reviewed by: robertchu
EXP-132. Extend model definitions and environments to allow users to specify PMML to use for model.

issue: https://jira.kiji.org/browse/EXP-132
review: https://review.kiji.org/r/1058