wddm,vboxtray: forward-port autoresize, multimon, and seamless fixes from 4.2 r87071, r87353, r87356, r87528, r87568, r87581, r87584, r87608, r87673, r87678, r87708, r87629, r87529; additional fixes
header (C) fixes
Main/Frontends: Also use facilities for guest features (seamless, graphics), added facility-state-to-name to VBoxManage, some renaming.
VBoxTray: New startup code, more detailed VBoxTray status-to-host reporting, cleaned up error handling, some renaming.
VBoxTray: Implemented global message registration/handling mechanism, added a global message for sending external messages to the systray balloon, refactoring, some bugfixes.
VBoxTray: Cleaning up, refactoring, grouping window messages.