bin/inspector: Add -h -v --version options

Refactor lib/config and bin/inspector, split printHelpAndExit into
two parts. The first part is building the help message and stays in
lib/config as `config._describeOptions`. The second part (print and
exit) is moved to bin/inspector.

/to @sam-github Please review. Node Inspector uses "rc" for argv parsing, therefore we can't use optimist's "alias".
/cc @3y3