Remove all support for "Jar" as a job type (alias for "MapReduce")

This change removes all compatibility code to support legacy jobs
of type "Jar" and includes an alembic script to change the job
type of any existing "Jar" jobs to "MapReduce"

Closes-bug: #1272465
Change-Id: I0d2c8ceeb83bd0bdcda5ed21e84890a9d8c99aa3
Merge "Remove all support for "Jar" as a job type (alias for "MapReduce")"