CLJS-749: In cases where *clojurescript-version* is unbound (as when running from source), return empty string from (clojurescript-version) instead of ".".
CLJS-749: Append CLJS version to browser repl-env working directory to prevent issues when changing versions in a project.
CLJS-749: Ignore .repl-* given that CLJS version is appended by default.