Design Deep Data Structures Operations

[ilyash]

https://github.com/ngs-lang/ngs/wiki/Deep-Data-Structures-Manipulation-Design

Related: #419 - Add walk() method to traverse Arr, Hash and other containers in uniform way

[ilyash]

Related: #34 - serialization / de-serialization

[ilyash]

Enough of design and implementation was done for now. Implementation is the tr facility (in dev branch).

Future work will follow spotting more use cases.