Qt4ProjectManager: New TargetSetupPage

Rewrite the target setup page to look and baheve better.
Noteable better at:
- Disabling shadow building
- Deselecting whole targets
- Adding import directories

Api-wise, Targets derived from Qt4BaseTarget have two ways to customize
the targetsetuppage.

a) Reimplement availableBuildConfigurations
b) Leave createTargetSetupWidget and create(... Qt4TargetSetupWidget)
   in their default implementation. (Or only slightly customize like
   the desktop target does.)

Or:
a) Make a dummy implementation for availableBuildConfiguration
b) Replace createTargetSetupWidget and return your own widget
   (It should match the look and feel from the other widgets.)
   It needs to be derived from Qt4TargetSetupWidget
c) Also replace the create create(... Qt4TargetSetupWidget) function
   and set up the target anyway you want.