Merge lp://staging/~dyams/unity-2d/launcher-desaturation into lp://staging/unity-2d

Change description:
Added new property 'isDashActive' to launcherView. LauncherItem already has mouseArea with hoverEnabled = true.
By listening to these two property changes we can achieve the desired effect.
QML icons provider is informed about the desaturated icon by appending :desaturate string to the icon id. The desaturate and tint effect is not perfect yet. At the moment it is achieved through QIcon and QPixmap, Which might need further tuning though.

This work will be quite easier done once the dash and launcher are merged. Please hold off merging this one.

Currently this feature hardly depends on Dash. It is completely implemented inside launcher.
So I wonder how merging the dash and launcher would simplify this task! Unless there is going to be a significant change in launcher implementation though.

I was seeing that a big chunk of the diff was not going to be useful anymore in the future. Specifically the changes to:

=== modified file 'launcher/app/launcherview.h'
=== modified file 'launcher/app/launcherview.cpp'

Hey Florian, If you look at the change more closely, you might notice that there is a clear abstraction between launcher and dash notification.

<code>
connect(DashClient::instance(), SIGNAL(activePageChanged(const QString&)),SLOT(onDashActivePageChanged(const QString&)));
</code>

That is the only piece of change that informs the launcher about dash 'active' status.
So, there is not much change introduced in that regard.
If the above line is not required in future, We can remove/replace it any time.