kiji-express-examples: EXP-313. Update Express Examples to reflect Cell name change to FlowCell

issue: https://jira.kiji.org/browse/EXP-313
review: https://review.kiji.org/r/1395
commit: https://github.com/kijiproject/kiji-express-examples/commit/a279a401c3bea474b69ddef56c452adb9b7cc470