CREATE TABLE may return 0 on some DBMS, but false is always an indicator something's wrong

(all SimpleSAMLphp source code should be updated, not only this contribution)

By using an appropriate WHERE clause in the SQL statement,
we can avoid loading the whole dataset in getMetaData(),
which brings an welcome performance improvement with large
Metadata sets.

bugfix: Make sure the PDO and Serialize metadata storage handlers return metadata containing the 'entityid' key.

While investigating issue #393, we noticed that these two handlers don't enforce the entity ID of each entity to be set in the 'entityid' key of the metadata array (the Flatfile and XML handlers to enforce this). Since this is the way we propagate the entity ID (code using metadata won't necessarily have access to the key of the metadata array containing the entity ID, or such a thing might not even exist), we need to make sure the entity ID is set inside the array. Otherwise, if the metadata for an entity does not contain it directly, the 'ExpectedIssuer' would be set to null, an error recorded, and authentication would fail as the entity ID of the IdP issuing an assertion would not match.

Rename Utils\HTTP::getSelfHostWithoutPort() to Utils\HTTP::getSelfHostWithNonStandardPort(), change the logic, and reimplement Utils\HTTP::getSelfHost() to depend on use the former. Complete the tests to include the case of port 443 while using HTTPS.

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().

Created a central database class and updated the PDO MetaDataStorangeHandler to use it instead of its own database classes

Fixed bug with adding metadata where it would try to run an UPDATE against the SQL DB if an entry did not already exist.