cas 8.x-1.5

This release includes the following changes:

• Add a configurable path that users are sent to when login fails for any reason. This fixes a bug where users may get stuck in an infinite redirect loop on login failure: #3039526: Prevent authentication redirect loop during login failure
• Improve UX of manually adding individual CAS users: When using the normal Drupal account registration form, the "CAS Username" field is now only revealed when a new "Allow this user to login via CAS" checkbox is checked. It's also placed next to the normal Drupal username field instead of at the bottom of the form.
• Add a separate form for bulk-registering CAS users, just like we have in Drupal 7: #2724849: Create UI for bulk-adding CAS users
• Allow specifying custom error messages when there's a problem with login. The login success message can also be customized or completely removed: #3013524: Allow specifying custom error and login messages
• Fix a issue where forced login paths that included a "destination" parameter would not actually redirect to the CAS server for login: #3029612: CAS automatic login should respect existing destination parameter
• Clean up the settings form to improve readability of some fields and descriptions.
• Updated README to remove old information and add additional API information.