Add structpb to wkt list

[gnagel]

1. Add struct.proto to the list of generated types
2. Ignore goland config files

[gnagel]

The generated types don't quite match up, it's missing the internal types:

func (m *Value_NullValue) CloneVT() isValue_Kind {
  ...
}

func (m *Value_NumberValue) CloneVT() isValue_Kind {
  ...
}

func (m *Value_StringValue) CloneVT() isValue_Kind {
  ...
}

func (m *Value_BoolValue) CloneVT() isValue_Kind {
  ...
}

func (m *Value_StructValue) CloneVT() isValue_Kind {
  ...
}

func (m *Value_ListValue) CloneVT() isValue_Kind {
  ...
}