Bug Description

Update the Launcher reveal interaction to make it more intuitive to new users.

This update involves a number of changes. These individual setting tweaks and changes are all tracked in a single bug because they all need to land to deliver a coherent UX (we can't pick and choose to do some of the items listed here and not others).

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SYSTEM SETTINGS

- Introduce a applet to the Gnome Control Center called 'Unity Launcher'

- This applet includes a single control that allows the user to select between "Show Launcher with mouse [ On left of screen | In top left corner ]

- 'On left of screen' becomes the default option

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'LEFT OF SCREEN' REVEAL

- When a user pushes the cursor *past* the edge of the screen the Launcher is revealed. To make this interaction insensitive and minimise false positives, the user must apply sustained pressure against the edge of the screen for a set length of time in order to reveal the launcher. Brushing on the side of the screen, or placing the cursor against the side of the screen should not reveal the Launcher.

- The 'top left' Launcher reveal stays (it does not conflict with the 'left of screen' Launcher reveal and is a complementary interaction).

- When the Launcher is hidden and a App issues an alert, the App icon should pop out and wobble from it's position in the Launcher. With the 'left of screen' Launcher reveal enabled, when the user moves their cursor to the position where the App icon pop'ed out, the Launcher will reveal giving the user direct access to the app.

(Note: this interaction was previously removed because it didn't work with the 'top left' reveal. When the user went back to where the icon had popped out of the Launcher, the Launcher didn't slide out leaving the user confused. With the change to the 'left of screen' Launcher reveal this app alert interaction can return. )

- When a application alert is outstanding, a blue triangle appears in the top left of the screen. The BFB no longer changes color. See attached design.

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'ONLY TOP LEFT CORNER' REVEAL

If the user changes the Launcher reveal setting to 'only top left corner' in appearance properties, the following changes happen:

- 'left of screen' Launcher reveal is disabled.

- The alert 'app icon pop out' behavior is disabled.