* fix bug with "K:":
  0) [K:something] in a voice applies to all voices. Instead abctool
     should remember which key we left the voice in the last time.
  1) If no key is given in the header none is assumed
  2) Any occurence of "K:" without any more text after that (like [K:]
     or K:\n) is assumed to mean "K:none".
  3) Any text in K: that is not relevant and therefore not understood
     by the transposition is simply added (unmodified) after the
     modified K:what-ever.
* accept incorrect keys (like C# or Db dorian) in transposition
* in K:none avoid removing superflurious acidentals
* if .abctool_check not present at first run, do only --check and
  write results to .abctool_check
* implement a way to not transpose certain voices
* install script
* implement conversion to chord, music-xml and WA
* have -g option (for "gui") which should bring up a simple dialog
  that let's the user set stuff like transpositon before viewing. This
  would be handy when abctool is associated with .abc-files in a file
  manager...  
* maybe have long options
* have -X Y option for selecting tune(s). Y should be N, N-N, where N
  is a number
* be able to match on composer/title (-C and -T) to select from
  multible tunes
* barfly macro expansion