* [golang] Add support for text parsing with json struct tags
Add struct tags to Go native structs generated when object API is used.
This allows to use the same JSON file as for C++ text
parsing(i.e. snake_case vs CamelCase) and thus enabling text parsing
for Go(when using object API).
* [golang] Add test for text parsing
Added small test to check and demonstrate text parsing in Go.
Also, ran clang-format on cpp file changes.
* [go] always write required types
* support optional scalars in go
* generate optional_scalars and monster_test
* restore original behavior for non-optional scalars
* add tests
