'milk add' raise AddError
Fix MilkodeYaml#package_root  bug

Return correct value in following packages example
  /path/to/pack
  /path/to/pack/sub
Add 'milk config -h' text
'milk ignore --global' can use at out of package dir.
set Updater#global_ignore & update_with_ctags  in web update.
Prepare 1.2.0