Native Json output

We can now get data in json format directly from the database by calling getJson on a molecule. So instead of converting tuples of data to json with some 3rd party library we can call getJson and pass the json data string directly to an Angular table for instance.

Internally, Molecule builds the json string in a StringBuffer directly from the raw data coming from Datomic
(with regards to types being quoted or not). This should make it the fastest way of supplying json data when needed.

Flat data

Normal "flat" molecules creates json with a row on each line in the output:

Person.name.age.getJson ===
  """[
    |{"name": "Fred", "age": 38},
    |{"name": "Lisa", "age": 35}
    |]""".stripMargin

Composite data

Composite data has potential field name clashes so each sub part of the composite is rendered
as a separate json object tied together in an array for each row:

m(Person.name.age ~ Category.name.importance).getJson ===
  """[
    |[{"name": "Fred", "age": 38}, {"name": "Marketing", "importance": 6}],
    |[{"name": "Lisa", "age": 35}, {"name": "Management", "importance": 7}]
    |]""".stripMargin

Note how a field name appears in each sub object. Since the molecule is defined in client code it is presumed that
the semantics of eventual duplicate field names are also handled by client code.

Nested data

Nested date is rendered as a json array with json objects for each nested row:

(Invoice.no.customer.InvoiceLines * InvoiceLine.item.qty.amount).getJson ===
  """[
    |{"no": 1, "customer": "Johnson", "invoiceLines": [
    |   {"item": "apples", "qty": 10, "amount": 12.0},
    |   {"item": "oranges", "qty": 7, "amount": 3.5}]},
    |{"no": 2, "customer": "Benson", "invoiceLines": [
    |   {"item": "bananas", "qty": 3, "amount": 3.0},
    |   {"item": "oranges", "qty": 1, "amount": 0.5}]}
    |]""".stripMargin