Use a single --trace command-line option for most traces

[edreamleo]

As of rev 337a2f there are now only three --trace options:

  --trace=coloring,drawing,events,focus,gnx,ipython,
          keys,plugins,select,shutdown,startup,themes
                        add one or more strings to g.app.debug
  --trace-binding=KEY   trace commands bound to a key
  --trace-setting=NAME  trace where named setting is set

For example:

leo --trace=keys,select