clojure: ensure correct node-nrepl version
clojure server: implementing more nrepl methods
clojure client: introducing clojure environments to allow interaction
with multiple clojure servers. Also supporting sessions (multiple
isolated "workspaces" per server) and tracking eval id. + adding support
for interrupting evals.
clojure client: shortcut for eval interrupt (cmd-. as in Squeak)
clojure client: improved stop-server