Fix some more phpdoc issues with returned values. Add a getLastError() method to retrieve information about the last error occurred.

Reformat the PHP authproc filter. Add a new 'function' option that allows to define an anonymous function. Deprecated the old 'code' function. Add tests.

Move the DatabaseTest to tests/lib/SimpleSAML/ where it belongs. Reformat code. Fix a few issues with phpdoc. Removed some unused variable. Use typed methos from SimpleSAML_Configuration instead of getValue().

INCPREFIX has been added in March 2008 and was already deprecated in June 2008, i.e. > 7 years ago.

Fix build: given that username and password are optional for some PDO drivers, do not enforce them to be set in the configuration. Use null as a default value for them.

Merge branch 'feature/pdometadata' of https://github.com/tdiscuit/simplesamlphp into tdiscuit-feature/pdometadata