* [CHD-3371] [Setup/Custom Fieldsets] Custom fieldsets can now be managed from the Setup->Custom Fields section.
* [Calendars/Virtual Attendants] Added Virtual Attendant macros for Calendar records.  This allows the creation of behaviors that are aware of calendar-wide automatically generated events (e.g. worklist, recurring).
* [Calendars/Snippets/Code Cleanup] Fixed a few issues with lazy loading calendar event data from snippets.
* [Virtual Attendants/Mail] Added the ability to use ticket_initial_message_* and ticket_latest_message_* placeholders in 'Before sending worker reply' behaviors.
6.4.2-checkpoint
Merge branch '6.4.2' into stable