[erp5_notebook]: add workflow to notebook, same as web page. add erp5_dms as dependency, load iodide notebook in notebook module, change indentation of gadget_officejs_jio_notebook.js, update security settings

erp5/util/testnode, scalability_test: Stop using a dummy frontend master and use host.vifib.net frontend with a valid SSL certificate instead. Always use https.

erp5/util/testnode: hosting subscription url was not updated once it was set. As a result, since testnode watched an old destroyed instance, the next test never started. Thus don't store hosting subscription url. It changes from time to time.

* erp5_core: allow to use Base_download from ERP5JS dialog
* erp5_base/dms* move Document_viewDownloadDialog into erp5_base
* erp5_base: add a dialog to download Image.
* erp5_web_renderjs_ui_test: test Dms download actions
* erp5_dms: allow to download original/converted documents from ERP5JS UI

erp5configurator: ConfiguratorItemMixin should not inherit Base class. Because of this wrong inheritance, configurator item classes did not work as Folder.

This is a workaround fix. Don't store uid issued by an external system in business template, it is not portable. Reindexing will fail. But I don't understand why those objects have to be stored in this business template.

DiffTool depends on deepdiff library to calculate diff but this only
works for pure string cases. In all other cases, we manually create
unified diff from old and new value. This led to problem between
how to display diff for large multiline content and for single line
content.

Related issue on Bug Module: https://nexedi.erp5.net/bug_module/20180810-13FBEFD

We have this [Do Not Test Required In Field View Form](https://www.erp5.com/documentation/developer/guideline/module/erp5-Guideline.Module.Creation#do-not-test-required-in-field-view-form rule) rule:
> This kind of constraint should be defined in Constraints documents and should to be checked in workflow transitions.
>
> Checking a field as "required" can cause problems like not saving the data when the user clicks on the save button. The same applies to the use of External Validators scripts in fields.

Currency view was not respecting this, there was both required fields and external validator. 
Also, the external validator was using an incorrect way of getting the "context document", so it was not working on RenderJS UI.

We are removing required fields and validator here, because this should be implemented using constraints instead.  To somehow preserve the same behavior, a new constraint is added in `erp5_base` and enabled in `erp5_configurator_standard`. Custom projects probably want to enable this constraint, but (as far as I know) we don't enable constraint by default. 

This  `Base_uniqueReferenceInFolderValidator` was apparently not used anywhere else and not working anymore, so we are just removing it.


/reviewed-on nexedi/erp5!710

This is needed to keep using the translation gadget.
See nexedi/erp5@9d0b0878

   Changes on ERP5Security: Define getFacebookUserEntry to reduce code duplication
   Add facebook support for login and logout (optional) on erp5_core, xhtml and credentials.