YamlMember improvements

• Add native support of System.Guid serialization.
• Add properties to YamlMemberAttribute:
  • Order: specifies the order of the members when they are serialized.
  • Alias: instructs the deserializer to use a different field name for serialization.
• The YamlAliasAttribute is now obsolete. New code should use YamlMemberAttribute instead.
• Throw proper exceptions, with correct marks, when deserialization of a node fails.