my pullrequests: line up controller/template handling with repo pullrequests

Currently, the data for 'my pullrequests' is loaded dynamically through
ajax, unlike the way 'repository pullrequests' are loaded (statically).

As there is no good reason to have both treated differently, and as dynamic
loading of 'my pullrequests' is not really needed, rework the handling of
the 'my pullrequests' page with the 'repository pullrequests' page.

This includes lining up the 'show closed pull requests' checkbox/link.

This also fixes issue #102 ('my pull requests' when not logged in:
incorrect handling of login).