Improved handling of strategy results in optimizer.

[micmicmichael]

• Now you can define how the strategy results should be handled (instead of just choosing the best result), then both server and worker will use that definition to handle strategy results.
• Changed the way of defining strategies from inheritance to composition.

[micmicmichael]

Feel free to raise any questions, thanks!

[micmicmichael]

Sorry for those careless commits.