Pass SimpleITK_* CMake variable from superbuild to external project

To remote the git hash from the nightly builds, the CMake variable
SimpleITK_BUILD_DISTRIBUTE needs to be defined in the actual SimpleITK
project. This is now accomplished introspectively examining and
passing all CMake variables which begin with SimpleITK_ from the
superbuild to the SimpleITK sub-project.

Change-Id: I1d83ab54797c05012155f74abb6bc7f025032e07
Tweak message for variables passed to ITK sub-project

Change-Id: I1e1c44dfe116a21e9794a2c166a6d667c819ab8c
Pass Python build variables to ITK from superbuild

Change-Id: Ice2554e1c6917597a876542f7fc112ee00339aa6
Moved include of language options before ITK external

This should ensure the python variable are defined for ITK when
wrap ITK is enabled.

Change-Id: Iccafb2036ee85e1af81203cd8bd1c3cda790704f
Merge topic 'DashboardFixes'

8cf1fe1 Moved include of language options before ITK external
b576084 Pass Python build variables to ITK from superbuild
Merge topic 'SIMPLEITK-349_RemoveGitHashFromNighlties'

a4a798b Tweak message for variables passed to ITK sub-project
8272ed5 Pass SimpleITK_* CMake variable from superbuild to external project