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

Migrate to Dropbox API v2

Root parameter is removed, as it must be now configured on dropbox website itself.

Thanks to Sven Franck <sven.franck@nexedi.com> for his original work on this topic.

Fix getAttachment when blob is undefined

/reviewed-on !74

Add facebook storage.
Keyless queries are case insensitive (like a fulltext search could be).

/reviewed-on nexedi/jio!68

/reviewed-on nexedi/jio!66

This reverts commits
215a2cca
e391b71d
ddf61098
5d6e60dd
bafcf854

Add saferepair storage
Add scenario and scenario officejs in test

Support mixed queries and add tests

/reviewed-on nexedi/jio!63

querystorage: add full text search
cryptostorage: fix confusing exemple

/reviewed-on nexedi/jio!62

ReplicateStorage: signature_hash_key is used also for attachments.
QueryStorage: support multiline text search.

/reviewed-on nexedi/jio!61