Feature Request: Add autofocus attribute to first column of "edit" and "add" views

[rob-hills]

Add and Edit model views generated by Flask-AppBuilder require the user to click on the first edit field of each form to move the focus there. Ideally the focus should automatically jump to the first field on the form.

The simplest fix for this would be to add an "autofocus" attribute to the first field on the form.

A nice-to-have extra feature would be two new attributes: "first_add_column" and "first_edit_column" that enabled the developer to specify (or override) which column on the respective forms was given the "autofocus" attribute.