Support for inputting ADT values for transitions

[anton-trunov]

This is a common problem for contact developers these days.

There is a wiki page with describing this issue further: https://github.com/Zilliqa/scilla/wiki/UI-design-for-inputting-ADT-values.

There is an external tool for that: https://github.com/Zilliqa/scilla-json-utils, but I think we should support this at the level of Scilla tooling.

This also should be integrated into the Scilla Web IDE.