Change AI processing to be more extensible
Add loadExternalAI
Use loadExternalAI
Definet the global "othello" variable
Add othello.registerAI
Add an example of external AI
Add forms to add new AI
Load external AI when it is added to lists
Add a feedback for loading an already loaded AI
Set a newly loaded AI to White automatically
Add a button to swap player types
Add fundamental API to deal with game trees
Add a more example of AI
Merge branch 'api'

Close gh-6.