with document storage

@seb, please review

/reviewed-on nexedi/jio!37

/reviewed-on nexedi/jio!35

This helps understanding why browser refuses to open the DB.

Example: Firefox prevent using IndexedDB if browser history is disabled.

/reviewed-on nexedi/jio!33

Fix ReplicateStorage to reduce conflicts during synchronisation.

Creation and modification process now use the same code

/reviewed-on nexedi/jio!29

/reviewed-on nexedi/jio!28

Do not display error in browser not implementing WebSQL.
WebSQLStorage will raise an error is used in such browsers.

JSON.stringify is not stable by design and can not be used to generate the hash.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify

This commit adds a stable version of JSON.stringify, available at jIO.util.stringify.
Relying on the nearly same string representation will simplify compatibility.

Tests were failing because some Firefox versions cannot
parse a specific date-string. So the Date constructor
that receives only integers was used. But there is one
details: this contructor uses months from 0 to 11, so if,
for example, we want to have a date in January, we send 0
as month and not 1.

Fix ERP5Storage to reduce conflicts during synchronisation.
ERP5Storage.get return a new parent_relative_url property which will lead to changes from ReplicateStorage point of view.

Fix QueryStorage/MemoryStorage bugs.

Copy all documents/attachments set in the storage, to prevent unwanting external modifications

This ensure that document created during synchro contains the same properties on local and remote storage.

portal_type attribute is not set anymore on getAttachment('person_module', 'view') json.
This remove duplicated code.

All time objects now are handled as local time, doesn’t the test runner
timezone. Also all queries tests that once used the native Date are now
using JIODate.

Webkit has issues when trying to load data-uri based images with
XMLHTTPRequest this is changed for the sake of compatibility with all
browsers.

Contains an ERPStorage fix.