ENH: Add Slice Annotations to DataProbe module

This commit enhance the DataProbe module providing an
easy way to show/hide/customize corner annotations, ruler and color bar in the
Slice viewers.

Associated setting are saved in the general settings common to
all version of Slicer installed on the workstation.

The implementation of slice view annotations in DataProbe is a part of QIICR Project [1] includes the following features:

• Corner text annotations including basic DICOM annotations.
• Interactive Color scalar bar widget for background and foreground volumes.
• Scaling ruler

[1] QIICR Slicer infrastructure projects

ENH: Add method vtkMRMLSliceLogic::GetForegroundWindowLevelAndRange

STYLE: Remove dead code

ENH: Added the following enhancements and fixes

• Added color scalar bar actors to color bar widget instead of adding it
  directly to renderer. The user can move the color bar now.
• The height of color bar is now sensitive to the top right annotations.
  When top right is deactive the height would be almost 100%
• Replaced the hard-coded UI with Qt Designer UI file.
• Fixed the vtk warning:
  vtkTextActor::SetInput was passed an uninitialized
  string
• Fixed issues with user settings
• An option added to have persistent background layer dicom annotation.
• Restore default values for all of the default settings was added.

ENH: Modified the logic to use dicom tag cache and the following fixes:

• Added dialog box for notifying slicer users about the new slice
  annotation feature
• Made Color Scalar bar off in default mode
• Code refactored in creating lines for ruler and other minor bugs fixed

From: Alireza Mehrtash <mehrtash@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23612 3bd1e089-480b-0410-8dfb-8563597acbee