Dialogs and checkboxes for two "accept invitation" fields

[Paul Everitt]

The accept invitation form (members.accept_invitation_view) has two required fields at the bottom. These are checkboxes with a link to a popup showing some text.

Wire these up using the newstyle forms:

- Two FormEncode "fields" defined in karl.views.baseforms, like username and the others. Most likely a boolean. There are UnicodeString fields already there for each of the two fields.

- Two "fieldwidgets" in karl.views.templates.formfields.pt that has the UI for each field. There are macros there already for each field.

- In the view function, inline some placeholder HTML. That will later be a lookup to the KSA (KARL Site Administrator) that gets the legal text content for each KARL.

- Pass the text into the form-rendering (before the page rendering) for each dialog, using keyword arguments for the text.

- Get jQuery UI dialogs that show each popup, with a single OK button.

[Balazs Ree (ree)]

I _think_ it's all done. Please reopen / comment if something is missing or not in the desired state.