[#121] Fix borked migrations

Replace migration 0032 to change empty string values in
Organisation.iati_org_id to NULL values to prepare for the unique
constraint on the field.

Add schema migration 0033 to set the unique constraint on
Organisation.iati_org_id and to create the InternalOrganisationID model.

Add data migration 0034 to add custom data to Cordaid and DGIS
organisation objects
[#121] Fix problems in IATIPartnershipResource

Many organisations were not created correctly when importing the
Cordaid XML. Turns out that XSLT sometimes truncates strings
incorrectly so a string that's supposed to be max 25 characters long is
26 chars!

Solve this by truncating too long organisation names in
IATIProjectResource.alter_deserialized_detail_data(). Seems
alter_deserialized_detail_data is only called on the "base" resource,
i.e. the one we're posting to, and not any related resources that also
recieve data through the post. So we have to sanitize everthing here.
This should be done more thoroughly, ideally trimming all char fields
and any text fields that aren't unlimited.

HACK: Change the signal creating PublishingStatus objects so all
projects are set to published.