Can Warn Staff 2.3.1

• Fix Forum reply-ban support

• Require php 7.2+
• Require XenForo 2.2+
• Require StandardLib v1.18.0+
• Fix allowing editing expiry of expired warnings
• Support Forum reply-ban by xon add-on (paid)

• Require Standard Library by Xon v1.16.0+
• Move some permission handling code into StandardLib so it has a common hook point