support for WTForms >= 3.0

Updated hybrid property detection to new sqlalchemy API

Modified hybrid property example to make use of the scaffold mechanism to create filters.

support multiple column sort with column_sortable_list

Update actions.js

Fix url generation with localized named filters.

Create function to toggle row checkbox if all checkboxes were toggled manually

Support single table inheritance for inline models (sqla)

Enable support for after_model_ actions in appengine

Support form_args for appengine

This is needed for export function to work

Coremabu

Add scaffold_list_form to allow edit in list view

Convert readthedocs links for their .org -> .io migration for hosted projects

As per [their blog post of the 27th April](https://blog.readthedocs.com/securing-subdomains/) ‘Securing subdomains’:

> Starting today, Read the Docs will start hosting projects from subdomains on the domain readthedocs.io, instead of on readthedocs.org. This change addresses some security concerns around site cookies while hosting user generated data on the same domain as our dashboard.

Test Plan: Manually visited all the links I’ve modified.