log: show recipe or cooker logs

Depending on the arguments, show either the log for a specific recipe/task, the
log for the latest task performed by a recipe, or the latest cooker log.

Signed-off-by: Ross Burton <ross.burton@intel.com>
contents: show the contents of packages generated by a recipe

Signed-off-by: Ross Burton <ross.burton@intel.com>
Merge remote-tracking branch 'rossburton/master'

* rossburton/master:
  contents: show the contents of packages generated by a recipe
  log: show recipe or cooker logs
README.md: update search, add log,contents,list

Signed-off-by: Christopher Larson <chris_larson@mentor.com>