Finalize rewrite of IMP_Maillog system

+ Now based on Mailbox/UIDs, not message IDs
+ Don't use Horde_History_Log, since that is specific to a single driver
+ Move IMAP-flag based MDN checking into an IMP_Maillog driver
Bug #13021: Fix maillog when forwarding multiple messages

Serendipitous: Required the IMP_Maillog system to be rewritten to handle
this properly.
Reversed logic
Only allow basic forward action when multiple messages are selected
No reason to be including this on every access, since it will be pushed to the browser on every AJAX update