Update Containerfiles, start CLI tool.

+ Containerfiles: default to using g++.  Most of the dev machines aren't
  working with clang yet; until this is sorted out, they'll need to use
  g++.
+ Add script to determine if the git-tree is tagged.
+ Add basic CMake skeleton and start CLI tool.

.gitignore

@@ -0,0 +1,7 @@
+build
+cmake-build-*
+
+TAGS
+tags
+core*
+