File & readme tidy
Reorg serializer tests
Transactions CSV
Model refactoring to allow non-activity formats.

Models moved, all tests pass or skip
Filter tests pass
Re-added e2e tests
All e2e tests (apart from json) working
Transactions CSV: recepient countries & sectors
Tidy of serializer test code
Fixes from parsing real data
Quick updates to page size & formats
Tranaction CSV: transaction types
Transaction CSV - titles & desc
Parsing title & desc
Make xml parser incremenal
Filter transactions
API tests for transactions
Transaction CSV: sector filters
Transaction CSV: filer by participating org
Removed alembic (migrations don't make any sense any more