openid-connect-generic-fork

Adds Additional Validation & Fixes Redirect Back URL (#301)

* Adds Additional Validation & Fixes Redirect Back URL
- Adds URL request validation.
- Updates the way the redirect back URL is formed.

* Fixes Redirect URL Logic to Handle Subdirectory Installs
- Handles home page login for redirect back.
- Handles subpages login for redirect back.
- Handles non-permalink sites.

* Refactor Redirect URL Methods to Support All Uses
- Consolidates make_authentication_url & get_authentication_url.
- Fixes redirect client back support for login button and make
  authentication URL.