Add JSON package

[d-torrance]

This package translates back and forth between JSON data (given in strings or files) and Macaulay2 things. For example:

i2 : fromJSON "{\"foo\": [1, 2, 3], \"bar\": true}"

o2 = HashTable{bar => true     }
               foo => {1, 2, 3}

o2 : HashTable

i3 : toJSON oo

o3 = {"foo": [1, 2, 3], "bar": true}

It looks like this package might be useful for the the polymake interface (see the corresponding project). In the longer term, I'm planning on using it to develop a Macaulay2 language server.

[mikestillman]

@d-torrance Great! How much of the JSON standard did you include?

[d-torrance]

@d-torrance Great! How much of the JSON standard did you include?

All of it!