RequestedAttribute with FriendlyName in Metadata autogenerated for SP

Modification to permit the automatic metadata creation of an SP to produce a friendlyName for RequestedAttributes.

The current code works as follows. If authsources.php contains the following configuration:

'attributes' => array(
  'eppn' => 'urn:oid:1.3.6.1.4.1.5923.1.1.1.6',
  'mail' => 'urn:oid:0.9.2342.19200300.100.1.3',
  'o' => 'urn:oid:2.5.4.10',
  'cn' => 'urn:oid:2.5.4.3',
  'givenName' => 'urn:oid:2.5.4.42',
),

the metadata generator will produce the XML Metadata as follows:

  <md:RequestedAttribute FriendlyName="eppn" Name="urn:oid:1.3.6.1.4.1.5923.1.1.1.6" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" />
  <md:RequestedAttribute FriendlyName="mail" Name="urn:oid:0.9.2342.19200300.100.1.3" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" />
  <md:RequestedAttribute FriendlyName="o" Name="urn:oid:2.5.4.10" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" />
  <md:RequestedAttribute FriendlyName="cn" Name="urn:oid:2.5.4.3" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" />
  <md:RequestedAttribute FriendlyName="givenName" Name="urn:oid:2.5.4.42" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri" />