Don't gather the proxy.auth setting if we don't use it

(being respectful with occurences that might change the behaviour, i.e. default database prefixes)

SimpleSAML\Utils\Attributes::getExpectedAttribute(): Check if the attribute has any values, and raise an exception if not.

Refactor SimpleSAML\Utils\Arrays::normalizeAttributesArray() to SimpleSAML\Utils\Attributes::normalizeAttributesArray().

Reimplement \SimpleSAML\Utils\Crypto::aesDecrypt() and \SimpleSAML\Utils\Crypto::aesEncrypt() to use openssl instead of mcrypt. This removes the direct dependency on mcrypt and closes #228.

Move the aes[En|De]crypt() functionality in \SimpleSAML\Utils\Crypto to internal methods where the secret is passed as a parameter. Then we don't need a working configuration to test the functionality.

Moved logic pertaining to finding configdir to central location, added ability to set via environment variable

Raise InvalidArgumentException if $retryURL is not a string AND is not null

Fix the phpdoc for SimpleSAML\Utils\Random::generateID() and add a constant with the length of generated IDs.

inet_pton failure is captured later - silence so unit tests pass.

Use InvalidArgumentException instead of SimpleSAML_Error_Exception when dealing with wrong input parameters.

Move SimpleSAML_Utilities::resolveCert() to SimpleSAML\Utils\Config::getCertPath() and deprecate the former.

Deprecate SimpleSAML_Utilities::getDefaultEndpoint().

Move SimpleSAML_Utilities:: debugMessage() to SimpleSAML\Utils\HTTP::debugSAMLMessage() and deprecate the former.

Move SimpleSAML_Utilities:: checkCookie() to SimpleSAML\Utils\HTTP::checkSessionCookie() and deprecate the former.

SimpleSAML_Utilities::resolvePath was moved incorrectly to \SimpleSAML\Utils\HTTP instead of \SimpleSAML\Utils\System. Fix that.

Move SimpleSAML_Utilities:: redirectUntrustedURL() to SimpleSAML\Utils\HTTP:: redirectUntrustedURL() and deprecate the former.

Move SimpleSAML_Utilities:: checkURLAllowed() to SimpleSAML\Utils\HTTP:: checkURLAllowed() and deprecate the former.

Move SimpleSAML_Utilities:: redirectTrustedURL() to SimpleSAML\Utils\HTTP:: redirectTrustedURL() and deprecate the former.

Move SimpleSAML_Utilities:: setCookie() to SimpleSAML\Utils\HTTP:: setCookie() and deprecate the former.

Move the createPostRedirectLink(), postRedirect() and createHttpPostRedirectLink() methods in SimpleSAML_Utilities to \SimpleSAML\Utils\HTTP. The last one is made private, the others are renamed to submitPOSTData() and getPOSTRedirectURL(), respectively. Deprecate the three old ones.