Post Friction 2.15.1

• Harden how post friction options are saved to avoid unexpectedly resetting non-rendered options

• Fix admincp quicksearch could error when searching for /
• Adjust phrases used when "Bypass post friction restrictions" permission is granted

• Fix 'Undefined array key "warnOnMultiPostForThreadStarter"' error.
• Fix global defaults for "Only allow a single moderated reply"/"Warn on multiple posts for thread starter" options did not work

• Fix viewing an old thread did not include the error message for the thread being too old

• Require php 7.2+
• Require Standard Library by Xon v1.18.0+
• Add some in-request caching to avoid recomputing a thread's post friction configruation mutliple times
• Rework post-friction option definitions to be more easily extendable and easier to maintain.

• Revise various post friction warning messages
• Add "Accept post friction warning" permission to 'guest' user-group for posting-before-registering support (if it hasn't been assigned)

• Fix post friction warning banner being displayed for general thread errors (ie user posting to a thread which was just locked)

• Fix 'Warn on media' option not showing the 'accept post friction dialog' box on replying.

• Require XenForo 2.2+
• Recommend php 7.2+
• Fixed missing post friction log reasons for multi-posting and mostly-quotes
• Add "warn on media/url/image" post friction option, with admin-defined customizable per-forum phrase overriding
• Show old/locked thread post friction warnings to users with the 'Bypass post friction restrictions' permission

• Fix "Old thread cut-off" option with value of 0 didn't disable the old-thread warning
• Fix "Old thread cut-off" option could have a per-thread value applied when the per-thread configuration page suggested it shouldn't
• Fix type-juggling when forum-wide post-friction options are used
• Migrate threads which used old friction key values to the new versions