Model the GoogleTest build after SimpleITK. This fixes previous build
errors.

ENH: ELASTIX-9 Only access connections via component indexes; BUG: ELASTIX-9 ComponentExist() did not work

The ENH: We deliberately avoid using connection indexes, but instead
force the user to think in terms of components which is conceptually
simpler and results in less pointers being thrown around while
constructing the blueprint.

The BUG: Temporarily disable functionality for deleting component until
we find a god way of asserting that vertex exist before it is accessed.

ENH: ELASTIX-1 Add unit test XML report and test harness for handling configuring test data at test compile time

Test data can now be added by only placing a content link in the
Testing/Unit/Data/Input and Baseline folders. Prevously, the dev
also had to add the path of the content link to a CMake variable.