fixes
Whonix-Gateway: added /etc/sudoers.d/kdm to allow (re)starting/getting status without a password, required for /etc/profile.d/20_desktop.sh.
Check total RAM. If more than 512 -> start KDE. If less (like 128) -> do not
start KDE. This should be be quite convenient, because users with low RAM could
reduce RAM to 128 MB and even if they sometimes wanted to configure/check
something, they could assign 512 RAM and automagically boot into the graphical
KDE desktop.