Expose RegistrationInfo in parsed metadata

- Add test case
- Fix .gitignore since it ignored all metadata folders

Add AttributeValueMap Authentication Processing Filter and unittest. 

Add a temporary autoloader that allows loading old classes (SimpleSAML_Path_Something) that have already migrated to namespaces (SimpleSAML\Path\Something), while logging a warning. This commit requires to regenerate the composer autoloader with ./composer.phar dump-autoload.

Make the module autoloader to register class aliases for the classes that are migrated to namespaces, so that they are still accessible via the old name. This keeps everything working while migrating the classes.

Add a PSR-4 autoloader for modules. Now modules can declare their classes under the SimpleSAML\Module namespace.

Fix misplaced </tr> (2x)

The login-page would not verify as valid XHTML 1.0 Transitional

Bugfix. While SimpleSAML\Database::query() returns a PDOStatement, SimpleSAML\Database::exec() doesn't. Make both return an integer with the amount of rows affected. Add a return value to SimpleSAML_Metadata_MetadataStorageHandlerPdo::initDatabase().

Fix missing argument

This fixes:
[Tue Feb 16 13:50:09 2016] [error] [client 10.48.224.4] PHP Warning:  Missing argument 2 for SimpleSAML_Error_AuthSource::__construct(), called in /apps/simplesamlphp-bd-1.14.0/modules/negotiate/lib/Auth/Source/Negotiate.php on line 336 
[Tue Feb 16 13:50:09 2016] [error] [client 10.48.224.4] PHP Notice:  Undefined variable: reason in /apps/simplesamlphp-bd-1.14.0/lib/SimpleSAML/Error/AuthSource.php(31)

Avoid the PHP session handler to generate errors when we try to retrieve a session after the headers being sent to the browser.

Enhance the documentation for SimpleSAML\Locale\Language. Move all the configuration properties to the constructor, instead of the methods.

Add tests for SimpleSAML\Locale\Language::getDefaultLanguage() and fix other tests for the same class.