Introduce new quassel-common package to remove conflict between quassel-client and quassel-monolithic

Build Qt version of monolithic, rename quassel-client-small to quassel-client-qt to make it consistent with other KDE/Qt dual packages

One of the split packages already had an optdepends and now has two. But they
need to be a single list, and instead, one accidentally overwrote the other.

It's needed for the icons to show.

use HTTPS for url and source downloads

FTR, commands used to change arch=() and then verify the changes:

$ sed -Ei "/^arch=/{s/ *?['\"]?i686['\"]? *?//;s/ *$//}" */*/PKGBUILD*

$ grep -r i686 * | grep arch= | grep -v repos

$ svn diff | grep -A 1 ^-[^-] | grep -v -- -- | cut -c2- |
  while IFS=$'\n' read -r l1; IFS=$'\n' read -r l2; do
    echo "$l1 -> $l2"
  done | sort -u

+ add cmake flag to force SSL because the ssl detection is broken