EXP-77. Allow Hadoop -D flags to be passed from the command line.

This commit modifies the express script so that any left-justified
Hadoop -D flags the user specifies to their scripts or compiled jobs
are properly shuttled to Scalding's Tool, so they are properly
reflected in the configurations of jobs launched.

Reviewed by: robertchu
Updated release notes.
Update dependency versions for release.
[maven-release-plugin] prepare release kiji-express-0.5.0
[maven-release-plugin] prepare for next development iteration
EXP-78. Capture all errors when validating model
definitions and environments.

This commit captures and reports to the user all model
definition and environment validation errors.

Reviewed by: kiyan
EXP-93. Fixes bug in writing null values in the generic api.

Reviewed by: kiyan

issue: https://jira.kiji.org/EXP-93
EXP-96. Adds validation for KijiTaps before launching jobs.

review: https://review.kiji.org/r/728
issue: https://jira.kiji.org/EXP-96
EXP-100. Regression testing against latest KijiSchema/MR snapshots.
Avro defs of filters
Adds supports in data request
Add case classes for column filters
All tests passing,
Deals with Options nicely.
All tests passing