CHOP-55. KijiSlice is returned in tuples.
Replace missing with KijiSlice
Fix job assignment
Utf8 => String
fix tests
CHOP-22. Design how users interact with Entity IDs

This includes all types of entity ids, including composite.

issue: https://jira.kiji.org/browse/CHOP-22
review: https://review.kiji.org/r/181/
Start removing support for "suppress materialization"