Throw 404 for non-existent org for bulk_process

Fixes #1682
[#1817] Upgrade SQLAlchemy to 0.9.x

No changes needed in the CKAN code base, but it requires changes on vdm,
see this branch:

https://github.com/okfn/vdm/tree/sqlalchemy-0.9-support

Also upgraded sqlalchemy-migrate.
Merge branch 'master' into 1682-bulk-process
[#1682] Test that 404 is returned
[#1682] Fix pep8 issues
[#1817] Update requirements file now that vdm is on pypi
[#1921] implement resource_show with package_show
[#1878] make (org|group)_member_create return dictized membership
rebuild search indexes after tracking update
[#1873] setup template variables at start of member_new controller

If a validation error was thrown, then the template would be rendered
before these variables had been setup.
[#1682] clean up test code
pass start_date as parameter to execute()
Merge branch '1878-member_create_return_value' of https://github.com/joetsoi/ckan into joetsoi-1878-member_create_return_value
Merge branch 'joetsoi-1878-member_create_return_value'
Merge branch '1873-fix_group_member_controller' of https://github.com/joetsoi/ckan into joetsoi-1873-fix_group_member_controller
Merge branch 'joetsoi-1873-fix_group_member_controller'
[#1682] remove empty setup_class method
Merge branch '1682-bulk-process'
Merge pull request #1682 from ckan/1682-bulk-process

bulk_process page for non-existent organization throws Exception
Merge branch 'master' of github.com:ckan/ckan