ENH: Clean up CLIs and library exporting

This allows projects outside of TubeTK to easily build each of TubeTK's
applications or modules. It also improves linking against TubeTK's libraries.

Change-Id: I40d188cd98c44ed76d198a2c6db5f220e56ae0ed
ENH: Move TubeTKConfig.cmake to superbuild directory

Much like CTK, it is easier for other projects building TubeTK to look for
the TubeTKConfig.cmake in the superbuild directory instead of its inner build.
UseTubeTK.cmake and TubeTKTargets.cmake have been moved along as well.

Change-Id: I3c3f0679b73c38fef9f969b47038ab5bb146d6bb
ENH: Delete FindTubeTK.cmake

Find*.cmake should only be written to handle project's specific
configurations issues. Since TubeTK doesn't have any, the regular
find_package should be able to do its job without a FindTubeTK.cmake.

Change-Id: I33313034e12d6f1716690bd4742ce65bd60ebbe7