[dmctl.cc] Switch daemon args so it's easier to up-arrow (dmctl <daemon> start).
[dmctl.cc] Stop doing substring abbreviations for daemon ids.

It was a good idea in theory but in practice it turns out to be not be a
good win (I don't think I've ever used it) and it causes problems when you
have names like:

  greenfelt
  greenfelt-html

In that case "dmctl greenfelt restart" is ambiguous so you need the fully
qualified name to talk to that daemon.

A better overall solution would be to add bash-completion.
[daemon.*] Add log_file() function that returns the path for the daemon's log file.
[daemon-manager.cc] Add "logfile" command that returns the log file path back to dmctl.
[dmctl.cc] Redo command arg processing a bit so it's more understandable and expandable.
[dmctl.cc] Put a return on the end of a thrown error since locally thrown errors don't have returns.

(The ones coming back from daemon-manager over the socket *do*)
[dmctl.cc] Add "log" and "tail" commands that run $PAGER and "tail -f" on a daemon's log file, respectively.
[stringutil.h] In split(), make it so trailing commas don't create empty strings.

I can't actually remember why I made this change. It may be important or it
may be unnecessary churn...
[options.h] Add comment about flags
[options.h] Whitespace.
[options.h] Phrasing.
[options.cc] Support short argument bundling.
[options.cc] Add test suite.
[daemon.*] Remove socketfile option.

It proved to not be useful (I've not found a single use in 3 years).

(Closes: #4)
[bug-closed] Remove sockfile
[daemon.cc] Missed the main part of sockfile removal.
[daemon.cc] Fix warning.
[options.cc] Fix warning.