This field is intended to display not authored by the user, typically machine generated, technical text.
The text is displayed with a monospace font and spellchecker is disabled.

Do not close a panel before using it

Reduce the number of event listeners.

Ensure a new subgadget is declared when the panel is opened

Editor panel can be closed from the sort/filter buttons

Localization should be done by fetching the locales and provide it as parameter to toLocaleDateString.

Fixes: UnboundLocalError: local variable 'translated_portal_type' referenced before assignment

in ready step, indexeddb storage is not yet create, so translation gadget can't get
language setting

in ready step, indexeddb storage is not yet create, so translation gadget can't get
language setting

This fixes number of Jupyter bugs.

Tests passing here: 

https://nexedi.erp5.net/test_result_module/20161117-147BEEA9

/reviewed-on !198

Same as for commit c3450f14:
BTrees don't accept None as key anymore.