Use yearly figures on Need instead of monthly.

Create migration that converts to and from the new
yearly figures.
Bug fixes for Need data migration.

* Update name of user migrating data.
* Simplify update to one call instead of two.
* Not hardcoding need collection name.
* Not calling lambda operation on nil data.
* Fix collection query to only return records with old field name present.
Merge pull request #25 from alphagov/change-month-to-year

Use yearly figures on Need instead of monthly.