* [Setup/Mail/Reply-To/HTML] Reply-to addresses can now specify a default HTML template for outgoing mail. The template set on the default reply-to address is the global default.  When a group doesn't have its own HTML template it will default to the one on its reply-to address.
* [Mail/HTML/Usability] The upgrade script for 6.6 now automatically creates a default HTML template and associates it with the default reply-to address.  This allows HTML replies to "just work" without any manual configuration.
[Code Cleanup/Platform/HTML] Configured HTMLPurifier to allow base64 encoded inline images in HTML templates.  These should appear in IMG SRC="data:..." rather than CSS.
* [Virtual Attendants/Mail/HTML] The 'Send mail' action in Virtual Attendant behaviors now supports sending messages using Markdown and HTML templates.
* [Virtual Attendants/Mail/HTML] The 'Send mail to recipients' action in Virtual Attendant behaviors now supports sending messages using Markdown and HTML templates.
[Code Cleanup] CSS style resource versions
[Code Cleanup/Devblocks] DevblocksPlatform::stripHTML() should now more effectively convert deeply nested blockquotes to '>' prefixed text.
* [Mail/HTML/Reply] Workers can now optionally choose a specific HTML template when replying.  If nothing is selected, the current group/bucket's default is used.
* [Mail/HTML/Compose] Workers can now optionally choose a specific HTML template when composing a new message.  If nothing is selected, the given group/bucket's default is used.
[Code Cleanup/HTML] Fixed a bug in Setup->Mail->HTML where editing an existing HTML template added a new blank line to the end of the content.
* [Mail/HTML/Broadcast/Tickets] Workers can now optionally choose a specific HTML template when broadcasting from ticket worklists.  If nothing is selected, the default for the group/bucket is used instead.
* [Mail/HTML/Broadcast/Addresses] Workers can now optionally choose a specific HTML template when broadcasting from email address worklists.  If nothing is selected, the default for the given group/bucket is used instead.
* [Mail/HTML/Broadcast/CRM/Opps] Workers can now optionally choose a specific HTML template when broadcasting from opportunity worklists.  If nothing is selected, the default for the group/bucket is used instead.
6.6-dev checkpoint