factor out TARGET_FORMAT
Change the nature of RunBundles to make them more general and more like
MakeBundles in that we have an arbitrary collection of targets, not just a
program_target and a input_target.
Now you can type:
  cl run date
  cl program:svmlight input:wine 'program/run input output'
  cl :svmlight :wine 'svmlight/run wine output'