ENH: Add itkmodular_common dashboard script
ENH: Teach itkmodular_common to finish up with a non-modular build

Some portions of ITK do not lie in any module.  The Examples build
outside of all modules.  The 'Install' test runs outside of all modules.
Tests outside of modules get the label 'ITKModular'.  After finishing
the loop over all modules do one final configure/build/test/submit
round that builds everything and runs the non-modular tests.
ENH: Build Examples during final all-modules build

Since the Examples directory depends on most modules ITK now requires
ITK_BUILD_ALL_MODULES to be ON to build it.  Keep BUILD_EXAMPLES off
during the initial configuration and during the configuration of each
module's subproject build.  Then enable BUILD_EXAMPLES during the final
monolithic build when ITK_BUILD_ALL_MODULES is ON.  This approach also
prevents any configuration errors in the Examples directory from
affecting the subproject build for each module.
ENH: Request only one module at a time

During a modular dashboard we loop over each module to build it as a
subproject dashboard submission.  We enable each module by adding

  -DModule_${subproj}:BOOL=ON

to the configuration line to explicitly request it.  Add also an option
to turn OFF the module enabled on the previous loop iteration.  That way
we configure only one module at a time (plus its dependencies) instead
of accumulating them.
ENH: Allow includer of itk_common.cmake to define CTEST_USE_LAUNCHERS

Thanks to Arnaud for the patch.
ENH: Teach itk_common to store ExternalData persistently

Set ExternalData_OBJECT_STORES to a location outside the source and
build trees.  The location will persist across multiple runs and be
shared by all builds in the same dashboard root directory.  Since the
content of the directory is content-addressed and the objects are
stateless this should not affect test results.  It will however avoid
duplicate downloads reduce cases of problems due to network failure.
ENH: Teach itkmodular_common to store ExternalData persistently

Set ExternalData_OBJECT_STORES to a location outside the source and
build trees.  The location will persist across multiple runs and be
shared by all builds in the same dashboard root directory.  Since the
content of the directory is content-addressed and the objects are
stateless this should not affect test results.  It will however avoid
duplicate downloads reduce cases of problems due to network failure.
DOC: Add LICENSE, NOTICE, and source header notices

The ITK dashboard scripts come with the same license as the rest of ITK.
ENH: Add to itk_common a hook after ctest_start

Add a "dashboard_hook_started" hook after the ctest_start call.
This gives scripts a chance to override the submission information
that ctest_start loaded from the project's CTestConfig.cmake file.
ENH: Drop unused itkmodular_common script

The ITKModular dashboard has no submissions and is not monitored.
Drop the client-side script supporting it.
BUG: Update CDash URL.

Change-Id: I5ef11e6a4d6a7fef9cc240419ba44988daa8e0ef
ENH: Add documentation for allowing only a specific target to be built

CTEST_BUILD_TARGET is a CTest special variable that accepts the name of a
specific build target, to be built instead of the implied "all".

CTEST_BUILD_TARGET only works if CTEST_BUILD_COMMAND is not defined (which
it typically isn't for ITK dashboard builds).

Change-Id: I3f54f38e20e7d476b763d82be428a7e8a498c971
ENH: Allow ExternalData path to be set by environment on dashboards

The new priority for setting the value of "ExternalData_OBJECT_STORES"
that is passed to any new ITK build is:
1. A CMake variable in the client configuration, "ExternalData_OBJECT_STORES"
2. An environment variable, "ExternalData_OBJECT_STORES"
3. The path "${CTEST_DASHBOARD_ROOT}/${dashboard_data_name}"
4. The path "${CTEST_DASHBOARD_ROOT}/ExternalData"

Change-Id: Ifb2b1bf07c114efb21b18c8fca615f7589ef5715
ENH: adding optional arguments for ctest_memcheck and ctest_converage

Change-Id: Ic2061a9a787d441e748ec86771261fa6fb5d7791
BUG: fix spelling of variable passed to ctest_memcheck

Add additional variable to be printed at start of test to aid in
debugging and logging.