Reimplement getPreferredTranslation outside of IdPDisco so it's reusable
and much more complete. The new method will search the current, default
and fallback language for a displayable string in various metadata
fields. This should be much more complete and robust than previous
approches. Make it a Twig filter so it can also be used there.

* Migrate email utils to non-static

* Migrate http utils to non-static

* Migrate net utils to non-static

* Migrate random utils to non-static

* Migrate system utils to non-static

* Migrate time utils to non-static

* Migrate xml utils to non-static

* Upgrade notes

* Update test-framework

* Fix tests

Convert to our wrapper class for assertions

* Remove deprecated classes

* Remove support for certificate fingerprints

* Remove many deprecated methods and pieces of code

* Remove SAML1.1/Shib1.3 support

* Remove many superfluous annotations

* Update unit test to work with new PHPunit

Closes #1268 
Closes #1020 
Closes #431 
Closes #167 
Closes #151 

* Migrate assertions to Webmozart

* Raise minimum PHP version to 7.0

* Remove tests pre-PHP 7.2

* Upgrade dev dependencies

* Ignore tests for deprecated class

* Add typehints; not touching public API

* Remove none-array replacements-param; old behaviour from pre-1.4 release

* Psalm fixes

* Add upgrade notes

* PSR-12

PSR-12 compliancy

The NoPassive constructor requirest the first parameter to be a constant indicating whether the error is due to the requester or the responder. Therefore, passing only an error message is not a valid way to create a NoPassive object anymore.

Closes https://github.com/simplesamlphp/simplesamlphp/issues/962

Fix build as a side effect. When vimeo/psalm tries to resolve dependencies, it now fails with this.

Migrate the logout handlers to namespaces, change the base abstract class to be an interface instead.