Mockup data in Zencode Given

[jaromil]

Add a conf directive that automatically generates mockup contents for all Given directives, simulating the presence of correct input.

This feature will help to test scripts in the absence of inputs, passing all checks in the Given phase.

To be seen how to react to schemas, but in the case of strings and string dictionaries (most used in didroom) it will be immediately useful.

Closely related to Fuzzing PR, moves the fuzzying logic one step higher into Zencode.

[matteo-cristino]

I do not know how to do it, but if we have "types" for schemas, then we could use them for this puropose. Moreover this will be also super usefull for js introspect API that will be able to return a type for a schema improving user experience both on ncr and gemini (this API is used to automatically retrieve what user should pass in input to the contract)