* [Activity Log/Usability] Fixed an issue where some Activity Log entries were still being created with hardcoded actor permalinks.  These are now generated using a dynamic format which will adapt if Cerb is moved to a new base URL.
* [Activity Log/Migration] Fixed an issue in the 6.0.0 migration script where knowledgebase articles referenced in the Activity Log weren't converted to the new ctx:// URL format.
* [Activity Log/Migration] Fixed an issue in the 6.0.0 migration script where a query attempted to retrieve *all* of the Activity Log entries as a single resultset in order to convert them to a new format.  This could overwhelm the available PHP memory_limit and prevent an upgrade from completing.  These records are now broken up into chunks of 5,000 rows.
[Code Cleanup]
* [Workspaces/Migration] Fixed an issue from the 5.6.0 migration script where certain ticket worklist filters weren't fully converted to their newer counterparts.  This resulted in worklists with nameless filters on them which didn't filter as expected.  While these could be cleaned up manually after the upgrade, some Cerb instances have hundreds of worklists and this process would be tedious.  These rows will be converted properly for people migrating from a version earlier than 5.6.0, and the rows will be fixed retroactively for any later versions by the 6.5.4 upgrade script.
* [Development/POP3] Added a script to /install/extras/developers/ for running a mock POP3 server in order to debug esoteric issues (like sporadic 30+ second connection timeouts).  These conditions are harder to simulate with a live mail server.
6.5.4-dev checkpoint
* [Virtual Attendants/Migration] Fixed an issue in the 5.4.0 migration script where Group Inbox Routing rules were not properly converted to Virtual Attendant group behaviors if there was only a 'To/Cc' condition.
* [Virtual Attendants/Migration] The 5.4.0 migration script will now create separate 'To:' and 'Cc:' header checks when converting Group Inbox Routing 'To/Cc:' rules to Virtual Attendant behaviors.  Previously it just created a 'To:' header check.
* [Update/Plugin Library] Fixed an issue in 4.x and 5.x migrations where the Plugin Library attempted to download its updates before the 5.7.0 patch created its database tables.  This didn't interrupt the upgrade process, it just logged an error.
6.5.4-release checkpoint