Support the "friendly" rendering in python

[dhh1128]

Allow python objects to output the friendly rendering described at https://dhh1128.github.io/sgl/docs/renderings.html#human-friendly-text

[dhh1128]

Maybe allow them to read it, too?

Create methods to parallel to_json and from_json -- to_friendly and from_friendly, maybe?

[RieksJ]

Link doesn't exist. It is https://github.com/evernym/sgl/blob/master/docs/renderings.md#plain-english.

I think if you want to have a human friendly rendering, specifically for non-developers, the examples you give in the 'plain-english' section aren't going to be all that helpful to them, simply because they have to hallucinate to interpret the meanings of 'priv1' (even if they are more 'meaningful', such as 'school' or 'food' in the Mya use-case example).

I can imagine that some part of the grant language must be human readable, e.g. when - e.g. in the Mya use-case - Malcolm can read on its tablets what stuff to ask for, and what checks to make before dispensing a food ration. That implies that the grant language must also be human-interpretable. Maybe that requires some other syntax?