add sortMaps:bool option

[cryptix]

This starts the work on adding sortMap:bool to make it easy to create canonical map representations.

I had trouble resolving these two comments:

• Canonical CBOR encoding #4 (comment)
• sorting #61 (comment)

I don't really see the point in moving this to a different library. Since the comment on 4 was newer I just went ahead and did it to see how hard it would be.

My rationale for doing it this way would be:

• re-creating a map/object with sorted keys is not very memory efficient either
• it bubbles up the problem to parts of the stack that might not (want to) care about it
• this code already iterates over keys list anyway, so we just need to sort those

This surely needs more tests before it can be merged/released but I wanted to get a temp check before I spent too much time on this.