Show assigned issues/mr be default on dashboard

This was default before but now it fixed with providing assignee_id
parameter making url shareble and dont reset when other filters users.

Also this commit removes old methods that are not used any more.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'dashboard-fix-assignee' into 'master'

Dashboard: fix assignee filter and remove some old code

See merge request !1354