Implement URL `campaign/create-form/`.

This URL only supports the HTTP GET operation.
Add class CampaignTable.

Table can be used to generate an HTML table displaying information about
Campaign objects. The table is not fully fleshed out. It should contain a
"virtual" column containing links to several pages.

Also add module `tables` to test suite.
Flesh out class Campaign (a view)

Make the Campaign view capable of responding to HTTP GET and POST requests. Also
create template `campaign.html`.