vCard v4.0 parsing: SOUND and KEY not recognized as URI

[respiranto]

Version: 4.5.5

Per RFC 6350, SOUND and KEY should be recognized as of URI value type by default.

The value type of SOUND and KEY is wrongly determined as TEXT instead of URI if no value type is explicitly provided.

Note: For SOUND, URI is the only valid value type.

This is possibly related to #676.