Fix board pagination

TablePagination directive: Add support for a updateResults callback again,
which apparently was removed in favor of emitting WorkPackage-specific events.

Kept all the events and calling the callback on page and per-page change now.
Board pagination: Pass per_page parameter to API

Before, per_page was ineffective.
Angular pagination: Add default per_page value to options

I guess it doesn't make much sense having a value as default here
that a user later can't select again.