Merge branch '3.1' into 5.2

diff --cc com.woltlab.wcf/package.xml
Simple merge

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/condition/UserTrophyCondition.class.php
Simple merge