AIMA-Java 1.5.2-Chp17n21-Rewrite

All of the algorithms from Chapters 17 and 21 have been rewritten, this includes:

• 17.4 Value-Iteration
• 17.7 Policy-Iteration 
• 21.2 Passive-ADP-Agent
• 21.4 Passive-TD-Agent
• 21.8 Q-Learning-Agent 

In addition:

• Rewrote Cell World Environment (environment.cellworld) to be independent of use.
• Re-organized probability.hmm package.
• Minor optimization to FrequencyCounter implementation.
• Documentation clean up.

Enjoy!

Ciaran