Fixed incorrect result for obj.Value().MSI() getter

[geseq]

When an object is created as obj := objx.Map{...}
calling obj.Value().MSI() returns an empty map. It should return the object itself as map[string]interface{} instead

[hanzei]

Thanks for your contribution @earncef!
Your solution kind of fixes the problem but is a bit hacky because type_specific_codegen.go is an auto generated file. But this is fine.

[geseq]

I will also try and work on a better solution for the type_specific_codegen.go file

[hanzei]

I opened #70. You might want to look into this