Start migration script with Products.contentmigration
Merge branch 'master' into migrations

Conflicts:
	plone/app/contenttypes/browser/configure.zcml
Add a test for migrating documents
Add Products.contentmigration to [sources]
Move Product.contentmigration to extra_require
Merge branch 'master' into migrations
auto-checkout Product.contentmigrations
More tests for migration
Remove unused imports; whitespace cleanup
Isolate atct migration code to remove dependencies

move the atct migration code to .migration and change the browser view
to return an error message if we can not import Products.contentmigration
and thus not import .migration.
Migrate ATFile + tests
Migrate ATImage + tests
Migrate ATImages without image data
Migrate ATLink + tests
Migrate ATNewsItem + tests
rename migrate_NewsItems() - migrate_newsitems()
Call all migrate funcs in MigrateFromATContentTypes-View
Migrate document data, fix news item migration

* Migrate the document text
* Fix the NewsItem migration: Create RichtTextValues instead of saving
  the text directly.
Return output of the migration steps
Migrate ATFolder + tests