Add/allow hashmaps as one of the accepted Value types

[the-tourist-]

I don't know how difficult this is to implement, but having the ability to subnest hashmaps, allowing the use of hierachial dictionaries would make hashmaps a lot more powerful. As hashmaps works at the moment it is only going one layer deep, but in real world usage you would often want to have dictionaries of dictionaries (1st key, 2nd key...).