command-line pass * profile create does *not* include redundant '--init', inherited from parent app * --init message more verbose * include aliases in items scrubbed from the argv passed to the kernel from the frontend, now that unrecognized aliases throw a warning * remove plain/pure as aliases, leaving only bool flags * make <engine|controller>_launcher_class help message more verbose, including example values * engines inherit work_dir from launching ipcluster by default, rather than using profile_dir * unimportable launcher classes won't cause a crash in ipcluster