Conflicts:
	src/jio.storage/mappingstorage.js
	test/jio.storage/mappingstorage.tests.js
	test/tests.html

Conflicts:
	Gruntfile.js
	package.json
	src/jio.storage/erp5storage.js
	test/tests.html

Add support for ERP5's selection_dmain

jIO.util.stringify({y: null}) used to error. Now it behaves similarly
to JSON.stringify, returning '{"y":null}'.

/reviewed-on !80

Add HTTPStorage and ParserStorage (RSS/OPML).

Thanks to Alain Takoudjou <alain.takoudjou@nexedi.com> for his original work on this topic.

Headers are returned as the document json.
Body is returned as the 'enclosure' attachment.

Query extend key_schema to sort_on
querystorage: add schema to use key_schema