LocalArchive class

- Handle x-zip export responses
- Handle multipart/mixed attachment responses
- @todo: use the same archive class along with the MultiPartForm for
import and create attachment
LocalArchive to handle downloads and PUT

- Added LocalArchive class with a.tools.crud.new.archive Factory
- Changed the AgilityModelBase class to wrap a link in a list based on
attrSpecs
- Tested getAttachment, createAttachment and import/export actions with
the new logic