* [Mail/HTML/Broadcast] Implemented HTML message support in address worklist broadcasts from bulk update.
* [Mail/HTML/Broadcast] Implemented HTML message support in opportunity worklist broadcasts from bulk update.
[Code Cleanup] Escaped HTML in ticket worklist broadcast previews.
* [Mail/Usability/HTML] When generating a plaintext part from an HTML-only message, Cerb will now attempt to preserve whitespace in pre-formatted (PRE) and CODE blocks.
[Code Cleanup] DevblocksPlatform::stripHTML() now provides a $strip_whitespace argument.  This allows the function to also be used when generating HTML->Text mime parts.
[Code Cleanup] DevblocksPlatform::stripHTML() now condenses multiple linefeeds more efficiently.
* [Mail/Usability/HTML] When generating a plaintext part from an HTML-only message, Cerb will now attempts to prefix nested BLOCKQUOTE content with '>'.
* [Mail/HTML/Usability When sending HTML mail, Cerb will generate a new plaintext part that cleans up Markdown formatting.  This plaintext part is sent along with the HTML message (e.g. for mobile and automated mail readers), and it's also what's stored in the conversation history.
* [REVERT] [Platform/Popups/Usability] Popups no longer open up in the center of the browser window by default.  This was causing problems on popups that grow, since they could expand beyond the bottom of the window and constantly require being dragged into place.  Popups now display at the top so they have the full browser height to grow before they show a scrollbar.  When a popup is opened a position can be defined now, so popups that don't grow (like the file chooser) may still elect to show up in the center of the page.
6.6-dev checkpoint