Follow the suggestions of [draft-knodel-terminology-00](https://tools.ietf.org/id/draft-knodel-terminology-00.html)
and other language frameworks and replace the notion of master/slave
with a more neutral primary/secondary.

* 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 

Add a common use case to add entity categories - until now it's
hard for users to find SSP examples for how to do it.

* 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

This reverts commit 00716eb4.

Apparently, links to modules must have a "./" prefix.

Signed-off-by: Jaime Pérez Crespo <jaime.perez@uninett.no>

This includes instructions on how to use SimpleSAMLphp with the PHP session backend while you are using it too in your application, also with a custom session handler.

It wasn't immediately clear to me where to put the cert and private key when I went through these instructions recently, so I thought I'd propose a change to make the destination explicit.

Closes #1103