Launcher - Add Launcher reveal proximity effect hint

[John Lea]

--- The design ---

See http://design.canonical.com/2012/01/launcher-reveal-prototype/

The prototype is also available from http://design.canonical.com/the-toolkit/unity-multi-monitor-interactions/

I will describe the design below, but I am only really describing what is in the prototype so it is worth downloading it and having a play. Note that the prototype has issues when running on Precise, because the pointer trapping in the prototype conflicts with the Precise pointer trapping. But you can still test the Launcher reveal in the prototype by moving the pointer towards against the edge of the left most screen.

--- The behavior ---

1. Firstly there is a proximity effect as you move your pointer *close* to the launcher (a shadow starts to reveal). See prototype for exact behavour.

2. When the pointer reaches the edge of the screen, the user can continue pushing the pointer left. The further the pointer is pushed, the more the shadow reveals. This continues until the point where the launcher reveal is triggered. At this point the launcher snaps out.

--- Visual assets ---

The image itself is only 16x1. Stewart stretched the image vertically to the height of the Launcher, and paint with an opacity of 0.75

See attached file proxshadow.png

[Adolfo Jayme Barrientos (fitojb)]

Fix Released, no?