* Remove six for PY2 compatability since our dependencies are not, PY2
is legacy.
* Removed usages of utils from future/past libraries since they are
deprecated. This includes 'from __future__ ...' and 'from past...'
statements.
* Removed compatibility imports for PY2, switched from six imports to
standard library imports.
* Removed utils code blocks that handle operations depending on PY2/3
versions.
* Removed 'from __future__ ...' lines from templates/code generators
* Used PY3 syntaxes in place of PY2 compatible blocks. eg: metaclass
* add new docfield fetch_from - serves as add_fetch
* replace options.split with fetch_from.split
* copied data from options to fetch_from
* patch to update fetch_from for docfield, custom_field and property_setter
* update tests according to fetch_from change
