- on account.asset.asset form view, field method_time, in 'Depreciation Information'
  page: use radio widget instead (without it, you couldn't change the field)

- on account.asset.category form view: prorata field hidden when required, and set
  to false when method_time is on 'Ending Date'. (It was previously possible for
  the prorata to be true while the method_time was 'Ending Date', which is invalid)

Includes compatibility-change to website_forum: a selection(callable)
converted to a Selection(list) since that can easily be extended in the
new API.

Apparently leftover from when features got removed from the client.

Sometimes, the sidebar on quotation previews can overflow the footer
if the window height is too small. To prevent that, the position of
the sidebar is blocked before overflowing, thanks to affix.

Half the controllers were already in the new API, migrated the rest.