Assorted fixes (#47)

* Invokes the site tree fix from previous fixes.

* Adds a disclaimer noting that previous years’ accounts have not been carried over.

Fixes #43

* Adds proposal type to the proposal summary page.

Fixes #40

* Adds travel/accommodation assistance to the proposals page, but makes it only visible to speakers in the proposal, or review managers.

Fixes #41.
Fixes #42.

* Reduces a lot of the whitespace in the header and footer.

Fixes #44

* Proposals review page now shows information for every speaker on a proposal.

Fixes #45

* Makes sure that non_field_errors are displayed by forms.

Fixes #37