[Insight-developers] Remove Testing/Data submodule, require CMake 2.8.5 on Windows

[Brad King]

Hi Folks,

I'm preparing to remove the Testing/Data submodule and replace it with
a real subdirectory full of ExternalData content links.  My progress
reports are going here:

   https://itk.icts.uiowa.edu/jira/browse/ITK-2673

I temporarily published a topic branch for this change here:

   https://github.com/bradking/ITK/branches/convert-TestingData

There are two issues that must be resolved before we can merge this change
and finally drop use of submodules from ITK:

(1) Dashboard submissions must be updated to the new itk_common.cmake
as I requested here:

   http://www.itk.org/mailman/private/insight-developers/2011-September/020435.html

As of now only a few machines have been updated.

(2) There are many duplicate content links in the new tree because there
were many duplicate data files in Testing/Data.  These duplicates lead
to failures in parallel builds due to a bug in CMake's string(RANDOM)
command in CMake < 2.8.5.  Until now the only workaround has been to
avoid use of duplicate content links.  I propose instead to use a
workaround that reads /dev/urandom to get random data:

   http://review.source.kitware.com/#change,2849

which works on all non-Windows platforms.  The only drawback is that we
will have to start requiring CMake 2.8.5 on Windows.  The benefit is that
we can get rid of the Testing/Data submodule and not have to make DATA{}
references less readable by artificially combining duplicate objects.

Comments?
-Brad