Misc. neatens

[johnkerl]

I made a focused effort to get RFC4180 CSV, multi-character separators, and autoconfig (the latter mostly thanks to 0-wiz-0) delivered ASAP after the HN release announcement.

Following those are some lower-priority items which should be addressed before they turn into longer-term technical debt:

• Make all on-line-help output 80-character clean. Most of it is 120-character but some even wider than that.
• Delivery of usage messages should be standardized in all cases (mlr main as well as subcommands): when invoked with -h/--help, print to stdout and exit 0; when invoked due to unacceptable syntax, print to stderr and exit 1.
• Replace the two or three remaining manual-test ifdef-mains with unit-test code. (All the rest have already been done.)
• Subsubcommands for step/stats1/stats2 should have online help.

[johnkerl]

Resolved with yesterday's commits