update add-on forum link
Revert "use a new header key on qt5 to fix drawing bug"

This reverts commit e06312321896cfa5d9a080a60998bd8d4efa3b5a.
fix crashes and corruption in column headers

set all columns to interactive at once to work around qt5 issues
show main window on startup on mac

this causes a visible resize, but seems to fix the intermittent
beachball on startup issue
Merge branch 'master' of github.com:dae/anki