Remove scan_lacs fallback code looking at new_measures, closes #354.
Updated to latest versions of alembic, billiard, celery and kombu.

Disable CELERYD_FORCE_EXECV as per celery changelog warning.
Downgrade irc to 9.0 as 10.0 drop Python 2.6 support.
Give all celery queues a prefix to better distinguish them in Redis.

Retain queues with the old name for one release, to make sure we
process any remaining jobs in those queues.
Create Cell Area Table (#349)

- Create CellArea table
- Add model tests
- Migrate cell area data from cell table to cell_area