change Machine.access_root to www_root, Bag.path to Bag.absolute_filesystem_path, including tests, api, templates, import script. added some flake8/formatting updates, closes #161
Merge pull request #181 from gwu-libraries/t161-update-path-vars

change Machine.access_root to www_root, Bag.path to Bag.absolute_filesys...
Merge branch 'master' into t165-tweak-item-view
Additional check to see if an Item is linked to a collection or not.