Prefix Essentials featuring auto expiring prefixes and prefix filtering 2.3.6.1

Added sidebars to pages listing threads with a specific prefix.

• Rename option "Show Prefix group above the thread list for filtering" to "Show prefixes above the thread list for filtering"
• Add option "Group prefixes above the thread list for filtering"
• When "Show Prefix group above the node list for filtering" is enabled, show prefix counts in the various drop downs
• Display the prefixes in the drop-down with their given style

Users with lots of prefixes can choose to group prefixes above the thread list for filtering, which can greatly reduce the clutter of having lots of prefixes individually displayed.

We had just one customer get server errors with Prefix Essentials because he was running with New Posts as the option (instead of Forums) for the Forums default page. This has been fixed.

Version 2.4.1 brings a new admin-customisable action button to expire prefixes.
It's a prefix-specific button that lives at the top of the thread, usable by people who have permission to edit the thread.
Admin can set the button text and confirmation message text.
When pressed by the user, it performs the expiry actions set by admin.
In our case on AVForums, we use it for users to more easily change the prefix in their classified advert threads. So the button is set to change the prefix, which is actually identical to editing the thread and changing the prefix there, but it's an easier UI.

Expiring prefixes with no set expiration date were expiring unexpectedly. This is fixed.

Fix for a server error when editing thread titles under certain circumstances.

Prefixes can be set to expire and on expiry, several actions can be applied to the thread.

• Delete thread (remove from public view, not permanent delete)
• Lock thread
• Move thread to a pre-defined, admin selected forum
• Assign a different, admin selected prefix (including none - i.e. remove the prefix)

- Fix prefix counts displayed in a forum did not respect "view threads by others" permission when counting viewable threads

Not a big deal, but thanks to @Robert9 for spotting the issue.

• Require php7+
• Require XF2.1+, remove XF2.0 support
• Fix additional query per-forum view when "Show Prefix group above the thread list for filtering" option is disabled
• Fix prefix page total not caching as expected
• Fix RSS support on a fresh XF2.2 install (or an XF2.1 install which has pruned old files)

Bug fix. Remove prefixes from the Ignored Prefixes list in User Preferences which

• Are not assigned to any forums
• Are assigned to non-visible forums.