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 nexedi/jio!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

Speed up attachment replication by using a document property to check if there was a change.
The attachment content is NEVER checked, as this configuration expect the document to be modified when an attachment is created, modified or deleted.
In case of conflict, follow the document conflict resolution result.