Remove redundant CMAKE_GENERATOR parameter from CTK project

The 'CMAKE_GENERATOR' property is already added by calling
'superbuild_include_dependencies' and associating
'${CTK_EXTERNAL_PROJECT_ARGS}' with the project.

See #418
Tweak CTK_SUPERBUILD option description text.

See #418
Ensure code following superbuild_include_dependencies(CTK) is executed.

This commit ensured that code located after the call to
'superbuild_include_dependencies(<top-level-project>)' is executed.

Also fixes the test accordingly.

See #418
Properly display name of project with dependency found on the system.

Fix type introduced by commit 74d440c5.

See #418
Display optional project only when configuring top-level project

See #418
Merge branch '418-support-use-system-option'

* 418-support-use-system-option:
  Display optional project only when configuring top-level project
  Properly display name of project with dependency found on the system.
  Ensure code following superbuild_include_dependencies(CTK) is executed.
  Tweak CTK_SUPERBUILD option description text.
  Remove redundant CMAKE_GENERATOR parameter from CTK project