Merge branch '3.0' into 3.1

diff --cc wcfsetup/install/files/lib/system/condition/AbstractMultiCategoryCondition.class.php
Simple merge

diff --cc wcfsetup/install/files/lib/system/condition/AbstractMultiSelectCondition.class.php
Simple merge

diff --cc wcfsetup/install/files/lib/system/condition/AbstractSelectCondition.class.php
Simple merge

diff --cc wcfsetup/install/files/lib/system/condition/UserGroupCondition.class.php
Simple merge

diff --cc wcfsetup/install/files/lib/system/io/Tar.class.php
Simple merge