Milestone: Working implementation of rules

As of today I now having a working implementation of rules. There are still some details to be fleshed out, but the value derivation engine works.

http://www.platoai.com/plato1.18/

This represents a major milestone for a fledgling AI project: The ability to use rules to derive facts about the world using what it has already been told.

The two working examples are:

"My first name is Daniel"
"My last name is Bigham"
"What is my full name?"

And:

"I was born in Canada"
"What is my nationality?"

The next thing on my agenda is to be able to use math in rules. For example:

"I have two sisters"
"I don't have a brother"
"How many siblings do I have?"

rule:
  $1 is_a person
  $1 has(count:$2) sister
  $1 has(count:$3) brother
  $count = # $2 + $3
  -> $1 has(count:$count) sibling