* Do some required field enforcement.
* thankyou_date column header has changed to "Thank You Letter Date".  Be sure to correct in incoming documents.
* Include a recent db schema migration in the fresh install script.

Change-Id: I681960d2af28345657864b89f2e0f191b4d6b172
fail entire check import if required columns are missing

Change-Id: Ie289ea00c5fea5fcca2a2a3c727037a11cb7adeb
Merge branch 'master' of https://gerrit.wikimedia.org/r/wikimedia/fundraising/crm