Fix two user_saml problems

The user_saml app isn't fully working on OC 4.5.12. There are two issues that should be fixed by this PR:

* When setting up the module (inside the settings page), all you get is a `Token expired. Please, reload page` message. The request token seems to be missing from the settings page, so this PR adds it.
* The p() function isn't defined on OC 4.5.x, so the module just refuses to work. Now the app initialization method checks the OC version and defines p() if needed