EXP-67. Add support for Kiji kvstores in extractors and scorers.

issue: https://jira.kiji.org/browse/EXP-67
review: https://review.kiji.org/r/604
EXP-46. (P2) Allow express script to launch schema-shell.

This commit modifies the express script to launch kiji-schema-shell
with express modules preloaded.

Reviewed by: robertchu