* Create .appveyor.yml

* Fix tests for Windows platform

* Fix builtin webserver for Windows

* Properly kill process on Windows

Explicitly test a file that does not exist, as well as a preloaded one
Virtual test file names intented to be semantic but not collide.

A PHPUnit listener unsets SSP environmental variables and attempts
to restore globals.

Note that when normalising the directory separator, using
DIRECTORY_SEPARATOR causes tests to fail on non-Windows platforms
as its value is (correctly) "/".

Now we are finally using the 2.x branch of the SAML2 library, which was also migrated to use namespaces. Even though the library provides an autoloader that allows loading the classes with the old names using class aliasing, we need to do the migration in one commit (at least for most part of it). This is due to the way SimpleSAMLphp checks data types, using inheritance to check objects agains abstract or more general classes. Even though class aliasing works, there's no way to replicate those relationships, and type checks that use the old class names will fail because the aliases are virtually new classes that don't inherit from others.

Fix the tests to handle the new, more permissive behaviour of SimpleSAML_Configuration::getBaseURL(), and add tests for getBasePath() too.

Start using the new configuration exceptions, handling error situations that before led to blank pages or even worse.

Add more tests for SimpleSAML_Configuration::getDefaultEndpoint() and SimpleSAML\Utils\Config\Metadata::getDefaultEndpoint().

Make it possible to pre-load a configuration array into SimpleSAML_Configuration for subsequent calls to getInstance() to use it. This opens up for unit-testing code that calls SimpleSAML_Configuration::getInstance().

Add tests for most of the data retrieval functions. No tests
for the metadata functions present though.