Add an option to set the checkbox state by default

Patch applies cleanly and works as expected.

This is a very useful option and I hope it makes into a release.

I'm cautious about this change, since the risk profile for a user not consciously interacting with the checkbox is "User is inconvenienced if they forget to check it, and need to log in when revisiting the site" versus "User stays logged in on a shared system if they don't explicitly log out of their account"

It would be an awesome feature to have.
I am not sure to understand the issue blocking this.
Since the admin can configure the state and the duration of the session, that gives the admin to decide what the best security/convenience balance is.

Missing in the patch:
- Add the new setting to the config file and set it to false by default
- Add the new setting to the schema

Addressed the 2 missing items