Convert to our wrapper class for assertions

It's easiest prevented by adding a linebreak after the <code> tag. This is not
ideal but a quick fix.

* 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

Fix Japanese translations

PSR-12 compliancy

Fix Psalm-issues in the modules-directory

* updated catalan translations

The old mail class uses the built-in `mail` function in PHP, and builds a payload by itself using hard-coded HTML and MIME-snippets. Let's use a library for that; PHPMailer has new dependencies and does all the heavy lifting.

re-add it and fix all templates that depended on it being unset

We'll use it in the new admin interface. For now, we just fix the old hook so that translations work for strings stored in dictionaries in the hooking module.