Multi-monitor - When connecting a external display, auto-detect whether it is a projector/TV or monitor and set mode as either Mirror Displays or Extend desktop accordingly

Implement the following sub-sections from the "Multiple Monitors UX Specification Phase 1" to improve some of the external display connect and disconnect use cases.

https://docs.google.com/a/canonical.com/document/d/1aHvJ-iIw-59bXTYBmIhQqEx0za2h9jpFE_RhZ2VOvJc/edit?authkey=CJO5wPkH&hl=en_GB

To summarize the requested changes:

1. When a external display is connected for the first time, auto detect whether it is a monitor or a projector/TV
2. Display a 'extend or mirror' panel (in the Unity system panel style) that displays this auto-detected choice to the user and gives them the choice of confirming or changing this decision.

3. In addition, pressing Super+P or Fn+F5 should bring up the 'extend or mirror' panel

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For detailed designs see:

Inside section 2.1: Booting Up, read the following sub-sections:
- Default Configuration Panel
- Connecting to a Projector or TV

Section 2.2: Hot-Plug Connecting

Section 2.4: Display Setup Keyboard Shortcut

Section 4.1 Booting up With a New Display Connected (but ignore the "I am presenting, do not disturb" checkbox in step 5).

Section 4.3 Hot-plug Connecting a Projector for the First Time (again ignore the "I am presenting, do not disturb" checkbox)

Section 4.4 Hot-plug Disconnecting From a Projector in Mirrored Mode