* Initial pass as supporting ngraph_dist builds with both gcc and clang.  Includes deprecated targets to support Jenkins CI with old feature and development branches that may not have these changes.

* Added build_all, check_all, and install_all targets

* Broke build and check steps into separate make sections.  Each step already generated its own log.

* Updated README.md

* Fixed a bug in the docker build context, which was overly general and included the build directories.  This caused a loop where the docker images rebuilt into multi-gigabyte images after testing was run (yikes).  New context is the contrib/docker directory, which is tiny.  No more image rebuilds.

* Rename the docker image to be less generic, so that another tool doesn't accidentally use the same name

* Change compatibility target "make check_cpu" to run "make check_all", so that all builds are done.

* Add a conversion step to change the test-suite names for all unit tests, to include an indicator for what compiler was used for the builds (_gcc vs _clang).

* Unfortunately, modifying the test-suite name with compiler suffix did not show in Jenkins test results.  Now modifying classname instead.

* Switch builds to be RelWithDebInfo, which turns on optimization and includes debug symbols.  Remove verbose output when creating tarball, to reduce log fluff.