ENH: Update SimpleITK

Created by: jcfr

List of changes:

$ git shortlog  534787d..699ed4b --no-merges
Andras Lasso (1):
      Do not create /.git folder when the project is configured

Bradley Lowekamp (30):
      Work around CMP0054 warning
      Update ITK superbuild version to 4.12.1
      Move Doxygen download URL to https
      Wrapping IterativeInverseDisplacementFieldImageFilter
      Fix typo in Python version warning
      Relax testing tolerance for N4 to accommodate intel x86
      Fix R package data with SimpleITK_FORBID_DOWNLOADS enabled
      Add missing usage of type property for point_vec
      Print AdaptiveHistogramEqualization radius parameter
      Update to CircleCi2.0
      Replace configuration_file_build_time
      Use ccache and CircleCI cache to expedite re-builds
      Add CircleCI cache for the ExternalData
      Use scikit-builds's juint formatter for juint
      Disable Python version warning when WRAP_PYTHON is disabled.
      Add HelloWorld to the example index
      Update ITK superbuild version to 4.12.2
      Fix typeo for BigIntegerFix class name
      Support ITK's rename README.md file
      Add GetRegion to LabelStatisticsImageFilter
      Fix issue with multiple BigIntegerFix classes causing tests to fail
      Address sign to unsigned comparison warning
      Use named inputs for ConvolutionImageFilter
      Update FAQ url to read the docs
      Fix detection of "std" flag in CMAKE_CXX_FLAGS
      Pass CMake cxx standard variable to try compiles
      Doc try to set "-std" flag when CMake cxx standard flags are present
      Improve error message when configuration fails.
      Fix sign/unsigned comparison warning.
      Add missing parameter and measurements to RelabelComponentImageFilter

Dave Chen (2):
      Update Documentation.rst
      Initial checkin of smiley face example

David T. Chen (3):
      Initial checkin of HelloWorld example
      Changed cmake var to SimpleITK_TESTING_NOSHOW
      Initial check of Documentation.rst for HelloWorld