WIP: Segmentation fault when trying to access result image

This build fails because VectorContainer has a private default
constructor

Fix an issue with compilation of ITK v4.8.1 on Mac OS X
Add CMakeLists.txt to root folder

The new Travis infrastructure supports a new version of CMake which is
required by some of SuperBuild dependencies.

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.