Adds AttributeConsumingService to the metadata

Adds:

- ServiceName
- ServiceDescription
- RequestedAttributes

Example configuration:

```
  "passport": {
    "saml": {
      "path": "/saml/login/callback",
      "callbackUrl": "https://127.0.0.1:8081/saml/login/callback",
      "entryPoint": "https://openidp.feide.no/simplesaml/saml2/idp/SSOService.php",
      "issuer": "https://127.0.0.1:8081/saml2/entityid",
      "serviceName": "GEANT Cloud Catalogue",
      "serviceDescription": "GEANT Cloud Catalogue",
      "requestedAttributes":[
        {
          "FriendlyName": "eduPersonTargetedID",
          "Name": "urn:oid:1.3.6.1.4.1.5923.1.1.1.10",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "true"
        },
        {
          "FriendlyName": "eduPersonPrincipalName",
          "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",
          "isRequired": "true"
        },
        {
          "FriendlyName": "mail",
          "Name": "urn:oid:0.9.2342.19200300.100.1.3",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "false"
        },
        {
          "FriendlyName": "cn",
          "Name": "urn:oid:2.5.4.3",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "false"
        },
        {
          "FriendlyName": "displayName",
          "Name": "urn:oid:2.16.840.1.113730.3.1.241",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "false"
        },
        {
          "FriendlyName": "givenName",
          "Name": "urn:oid:2.5.4.42",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "false"
        },
        {
          "FriendlyName": "surname",
          "Name": "urn:oid:2.5.4.4",
          "NameFormat": "urn:oasis:names:tc:SAML:2.0:attrname-format:uri",
          "isRequired": "false"
        }
      ]
    }
  ,
```
Merge pull request #54 from skanct/metadata_for_attribute_consuming_service

Adds AttributeConsumingService to the metadata