[#52] add transaction_ref field to transaction.csv

  - add ref to Transaction model and migration adding ref field
  - parsing <transaction ref=*> and add transaction_ref to csv output
  - tests for parsing and output to csv
  - couple of gitignores
[#59] Alter (budget/transaction).value_amount to decimal

  - change budget and transaction model
  - alembic migration
  - Add iati_decimal function
  - Make budget.value_amount non-nullable
  - update budget tests and add transaction.value_amount tests
[#59] move aet-activities to fixtures folder
[#52] Merge branch '59-decimal-values' into 52-add-fields-to-transaction-csv

fix alembic migration revisions.
[#52] Add providing_org_ref and providing_org to transaction.csv

* add providing_org to transaction model + alembic migration
* parse providing_org in transaction xml
* providing_org and providing_org_ref output in transaction.csv
* tests for above
[#52] add crawler update single dataset command

This is only really needed for testing. Updating a single dataset
is much quicker than redoing the entire catalogue
[#52] add provider-org-activity-id field

This is just stored as a text field instead of a foreign key, we can't
guarantee that the activities would have been parsed properly or exist
so it's probably best to leave it as a text field

Renamed all providing* fields to provider*

Also removed the precision on numeric fields and fixed up the alembic
migrations
[#52] fix transaction_provider-org

Change transaction_provider-org to the content of the provider-org tag
rather than looking up the organisation name from the provider-org/@ref
attribute.

Combine the alembic revisions together
[#52] add receiver_org fields
[#52] csv transaction_value_currency and transaction_value_value-date

add transaction_value_currency and transaction_value_value-date to csv
output
[#52] Add description field to transaction.csv
[#52] Add missing fixtures
[#52] add flow, finance, aid, tied, disbursment fields

Add and update the relevant codelists csv files, update the transaction
models and parser to store the field types, add alembic migration added
relevant tests
Closes [#52] Add fields to by_sector, by_country csv view.

Added the fields to the 2 views in quite a hacky way, will need to be
refactored. Also added recipient-country and sector to some of the xml
fixtures I added. Tests work and test functionaility but need to be
 clean up.
[#53] Parse recipient-region tags

and and save to model, added iati_activity_JP.xml as a small test
fixture
Closes [#53] Add recipient-region(code/percentage) columns to csv
[#54] Add start/end_planned/actual date fields to csv
[#54] Add participating_org fields to activities.csv
Merge branch '54-activity-csv'

Conflicts:
	iati_datastore/iatilib/test/test_serializers/test_csv_activities.py
Merge branch '52-add-fields-to-transaction-csv'