Murphy hit me in the face

Closes https://github.com/simplesamlphp/simplesamlphp/pull/782

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

SHA-1 is still supported but needs to be configured explicitly if you need it.

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.

This reverts commit ef36c5fd.

All a bit too involved right before a planned release.

Also, convert to PSR-2 where that was still lacking in these files.

Support both hint.cidr and DiscoHints->IPHint

The equation was wrong.. exceeding means > not >=

* Support metadata XML directly in config
Also consider 'xml' as a key, in addition to 'url' and 'file'.
When provided, attempt to load this directly as a metadata XML string.
This is useful when working with dynamic configuration and external polling of metadata updates.

* Test loading XML from a fixed string
No preexisting test in this area
Adjust XML loader to only get global config in file mode - otherwise it is
unused, and it might pollute the test usage.
Test that an actully invalid config throws an exception, but that minimal valid
(albeit useless) XML is accepted.

Now using DiscoHints->IPHint to support specified SAML extension for IdP discovery

The use of count function is wrong and unnecessary. If the array is
empty the foreach loop will not run.

With a dynamic configuration, it is not desirable to load from literal files
By storing a configuration object against a filepath, subsequent calls to
getConfig work transparently, bypassing the disk load step.

Fixes https://github.com/simplesamlphp/simplesamlphp/issues/818

forward-port of my recent fix in branch 1.15

Fixes issue https://github.com/simplesamlphp/simplesamlphp/issues/793