Dictionary built-in type

Simulating with a 'dict' runtime library object.
Supported constructions:
d = dict(one=1, two=2)
d = {'p1': 'prop1'}
p = 'p1'; d = {p: 'prop1'}
d = {4: 'prop1'}
Supported operations: d[key], for key in d, len, clear, get, keys, pop,
values