move cas settings to settings dialog
Description
In this MR, I am moving the CAS settings to our settings dialog. I am still trying to address the scenario where a user has no backends installed, what will be in the Notebook menu, since we don't have the Configure CAS dialog anymore?
Conformity
[ ] Changelog entry[ ] Unit tests[ ] Update INSTALL[ ] Downport- Fixes:
When external dependencies are removed
[ ] Reporting to ...