EXP-345. Rename root and flow modules of Kiji Express

issue: https://jira.kiji.org/browse/EXP-345
review: https://review.kiji.org/r/1438
EXP-322. Touch up scaladocs of ColumnOutputSpec and its subclasses.

issue: https://jira.kiji.org/browse/EXP-322
review: https://review.kiji.org/r/1442
EXP-326. Seq[FlowCell]s from paged columns have unexpected behaviour

issue: https://jira.kiji.org/browse/EXP-326
review: https://review.kiji.org/r/1433
Add a relative project reference for the base project files

Signed-off-by: Caitlin Johnson <caitlin@wibidata.com>
EXP-344. Express needs integration tests

 - Plumbing for integration tests using AbstractKijiIntegrationTest.
 - Simple integration test.

issue: https://jira.kiji.org/browse/EXP-344
review: https://review.kiji.org/r/1434