Add ClueBat, CluePaddle and ClueByFour. Improve file structure and API.

[This is an updated version of the previous pull request #10. It moves the files into the correct dirs - general stuff in csharp_framework and AIs in entries, as well as fixing some other mistakes with the previous branch. It wasn't practical to update the other branch. Thanks]

Change Program structure so that we can make different bots at once.
This is to build multiple clients with different AIs in a single build step.

Add ClueBat, slightly more clueful than ClueStick.
Add a few enhancements to the ClueSharp types.
Add CluePaddle, a much more intelligent AI.
Add ClueByFour. - reasonable AI, without CluePaddle's powers of deduction.

Move framework files into csharp_framework, AI projects into entries.