Add BUILD_TESTING option allowing to submit configure and build to CDash

The option is automatically added by including the CTest module.
Add a CTest test for each python unittest.

The list of available unittests is hardcoded in the cmake/UnitTests.cmake
file and can be regenerated by building the "list_unittests" target.
Merge branch '8-add-ctestconfig'

* 8-add-ctestconfig:
  Add a CTest test for each python unittest.
  Add BUILD_TESTING option allowing to submit configure and build to CDash