Accept JSON schema as program metadata

[rathishcholarajan]

Summary

Accept JSON schema as program metadata and print it in human readable format in pprint_programs().

Details and comments

Fixes #44

[jyu00]

I don't think the new metadata format you're basing this on is correct, unless of course the API doc is wrong lol

[jyu00]

Can you show what the output of print(program) would look like for say sample-program with this new code? Using this input

{
  "name": "sample-program",
  "description": "A sample runtime program.",
  "max_execution_time": 300,
  "spec": {
    "backend_requirements": {
      "min_num_qubits": 5
    },
    "parameters": {
      "$schema": "https://json-schema.org/draft/2019-09/schema",
      "properties": {
        "iterations": {
          "type": "integer",
          "minimum": 0,
          "description": "Number of iterations to run. Each iteration generates a runs a random circuit."
        }
      },
      "required": [
        "iterations"
      ]
    },
    "return_values": {
      "$schema": "https://json-schema.org/draft/2019-09/schema",
      "description": "A string that says 'All done!'.",
      "type": "string"
    },
    "interim_results": {
      "$schema": "https://json-schema.org/draft/2019-09/schema",
      "properties": {
        "iteration": {
          "type": "integer",
          "description": "Iteration number."
        },
        "counts": {
          "description": "Histogram data of the circuit result.",
          "type": "object"
        }
      }
    }
  }
}

[rathishcholarajan]

Can you show what the output of print(program) would look like for say sample-program with this new code? Using this input

Output will look like this:

==================================================
sample-program:
  Name: sample-program
  Description: A sample runtime program.
  Creation date: 2021-05-10T08:59:51Z
  Update date: 2021-06-04T14:11:19Z
  Max execution time: 300
  Input parameters:
    Properties:
        - iterations:
            Type: integer
            Minimum: 0
            Description: Number of iterations to run. Each iteration generates a runs a random circuit.
            Required: True
  Interim results:
    Properties:
        - iteration:
            Type: integer
            Description: Iteration number.
            Required: False
        - counts:
            Description: Histogram data of the circuit result.
            Type: object
            Required: False
  Returns:
    Description: A string that says 'All done!'.
    Type: string

[jyu00]

A few minor comments but mostly looks good!

[jyu00]

Minor doc changes but otherwise looks good!