ENH: Simple MI metric evaluation

This is a simple program for mattes mutual information metric
evaluation over two input images and a BSpline transform.

If there is no input BSpline transform, the transform will be
set to Identity as the default.

The Usage:
./PerformTestMMI Image1 Image2 [BSplineTransformFile]
                 [NumberOfHistogramBins] [NumberOfSamples]
Merge pull request #82 from aghayoor/MIMetricEvalOnBSplineTrans

ENH: Simple MI metric evaluation
Update README
COMP: Fix compilation error

Clang compiler is very strict about which types can be added to ostream.
BUG: support new Philips scanner data.

Also include itkDCMTKFIleReader from ITK;
found a bug in thatclass in ITK,
so fix the bug and include the class here,
until the bug is merged in ITK proper.
COMP: Synchronize Superbuild with NAMICExternalProjects
COMP: fix some CMake 3 problems
COMP: make sure SlicerExecutionModel_DIR gets passed to BRAINSTOols
COMP: fix compile failures due to BRAINSTools not finding VTK
COMP: rearrange CMakeLists.txt to accomodate CMake 3
Merge pull request #83 from Chaircrusher/ArtichokeSuperbuild

Artichoke superbuild for BRAINSTools