+ Added SexpInterpreter since it is such a common pattern
[git-p4: depot-paths = "//src/sexp_processor/dev/": change = 8310]
+ Added aliases Sexp#head & Sexp#rest for readability
[git-p4: depot-paths = "//src/sexp_processor/dev/": change = 8311]
prepped for release
[git-p4: depot-paths = "//src/sexp_processor/dev/": change = 8312]