[FFe] Unity8 bugfixes for Zesty

We'd like to ask for a freeze exception for the packages in
silo https://bileto.ubuntu.com/#/ticket/2668

The silo contains bugfixes for the Unity8 session, significantly improving the experience:
- improve pointer vs. touch menu logic
- Bug 1675373: Pressing Super hides launcher
- Bug 1672053: [unity8] opening app drawer breaks Alt-Tab in app switcher
- Bug 1672673: Application menus should hide when triggering the spread
- Bug 1676995: [regression] App switcher does not respond to tab events
- Bug 1677259: [regression] Search string not replaced in app drawer after Super+A
- improve greeter visuals and behaviour
- Bug 1673199: Greeter shows "unknown" session if user has never logged in when it should show default.
- Bug 1666363: Windows behind are missing during un-maximize animation
- Bug 1668053: [unity8] It's impossible to close some dialogs (missing 'X' window button)
- Bug 1667570: App drawer icon titles are difficult to read (truncated too much and have no tooltips)
- Bug 1676878: Not using Ubuntu font family and suru icons in Qt widget apps
- Bug 1675448: Unity 8 doesn't allow multiple Mir connections from an application instance

The impact on the distribution is minimal, as limited to the early-look session based on Unity8.
The silo went through complete QA cycle, standard for all Unity8 development.
Britney was happy with it: https://bileto.ubuntu.com/excuses/2668/zesty.html