Fix Locale; If a Twig-variable is not set and then translated, these methods are called with a null parameter

* 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

* Use strict variables in Twig, except for our TemplateTest; throw exception on missing variables

* Fix issues due to Twig strict_variables=true

* Fix for #1229

* Fix metadata-template

* 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

* Ensure getConfig* functions can only return Configuration

* Cleanup after #1189

* Deprecate Configuration::getConfigList

The OASIS spec [SAML V2.0 Subject Identifier Attributes Profile](https://wiki.oasis-open.org/security/SAMLSubjectIDAttr) defines two new standard attributes intending to replace use of persistent NameIDs and the eduPersonTargetedID and eduPersonUniqueId SAML attributes. The updated Kantara [SAML V2.0 Interoperability Deployment Profile](https://kantarainitiative.github.io/SAMLprofiles/saml2int.html) will also standardize on these new attributes (cf. SDP-SP15 ibid.).

This commit adds the two new attributes:

* to the URN attribute maps
* to attribute definitions and translations of the locale system
* to the smartattributes:SmartID auth proc filter (after any other SAML attributes, but before the non-SAML ones).

Support for saml2int SDP-SP16 (attribute requirements signalling via Entity Attributes) is not included here.

This allows us to use this new filter to translate strings from a given array of translations, where every translation is indexed by its ISO 639 code. A new configuration option ('language' -> 'priorities') is available too to control the alternative languages that can be used instead of a given language, when the latter is not found. The filter returns null when no suitable translation is found, so that it can be combined with "default()" to set a default translation for a given string.

Add a couple of methods to perform translations with PHP's native gettext implementation, and start using them.

These two methods are equivalent to gettext/gettext's __() and n__(), but using strtr() instead of vsprintf(), so that the placeholders can be names instead of printf() format strings.

This makes instanciating the Translate/Template-class unnecessary.

For #455

For #455

Both have been migrated to use namespaces.

More bugfixes. The SimpleSAML\Locale\Language::$languageParameterName and SimpleSAML\Locale\Language::$language properties should be private, and therefore not accessed from the outside of their respective classes. Add getters instead.