'add' command

[SJAnderson]

add command that will automatically create a new page group (template, presenter, stylus, schema), create a new template, or create a new collection cson. This command will also add the new item to the package config.

ex.
dobi my-package@1.0 add collection event
dobi my-package@1.0 add page bio
dobi my-package@1.0 add region mobile-footer
dobi my-package@1.0 add template image-popup