Use Python json instead of deprecated Products.ERP5Type.JSON.
ERP5Form: Returned field default value for ListBox was not consistent with non-ListBox field.

So, Relation Fields in ListBox were ignored during validation as the input
value is compared with the current (default), thus the field could not be
cleared as the value from the actual object was not retrieved at all.
Likewise a non-ListBox field, call custom edit() if available (eg encapsulated editor).

For example, MultiRelationStringField does not return a plain value, but a
MultiRelationEditor overriding Base_edit default behavior.
Add support for Listbox for getting Relation field field parameter dict.
erp5_autocompletion_ui: Serialization of array was broken with ERP5.
erp5_autocompletion_ui: Increase delay before searching from 300ms (default) to 600ms, this should be enough...
erp5_autocompletion_ui: Clean up and make parameters names consistent with ERP5.
RelationField: Implement autocompletion and use it by default once erp5_autocompletion_ui is installed.
RelationField: Support older version of jQuery UI (<= 1.9) for autocompletion.
erp5_autocompletion_ui: Support properly Input Method Editor for autocompletion.
Limit the number of results to 15 instead of 20 as it seems to be enough (taken from an existing customer project).
erp5_autocompletion_list: Move away generic JS code from RelationField as it should be reusable anywhere.
erp5_autocompletion_ui: Allow customisation of object property being showed with autocompletion.

Possible through defining a TypeBasedMethod (PORTAL_TYPE_getCompletionDict)
returning a dict serialized in JSON by the calling method, or otherwise
overriding fallback script (Base_getCompletionDict).
erp5_autocompletion_ui: Rename ERP5Site_getCompletionList for naming consistency sake.
erp5_autocompletion_ui: Consider that description may not be needed, thus only one line, the label, is displayed.
erp5_autocompletion_ui: Autocompletion property value set to the field should be the one queried from the Catalog.
erp5_autocompletion_ui: Add JS ERP5Autocomplete() parameter to transform text before sending AJAX request.

For example, if one wants to uppercase/lowercase the value entered by
end-user.