modify models to have attributes on items, wrap for old models
adds upload support for fixtures with item attributes
added excel download for items-with-attributes
update web-edit-ui for item-attribute
make fixture XML output to have item-attributes
do not fail if there are no fields or no properties on a fixture-type
responding to PR (typos, style etc)
catch and report XML generation exception better and fix tests
Merge branch 'master' into fixture-prop
fix default value for uploads without attributes
cleanup and fix typo
remove debug raise
doc string --> comment
Merge pull request #4368 from dimagi/fixture-prop

Fixture prop