[Lua] Added Burrows-Wheeler Transform, Run-Length Encoding (and enhanced A-Star)

Hi awesome people,

Find in this PR two new algorithms widely used along with compression algorithms :
* [Burrows-Wheeler transform](http://en.wikipedia.org/wiki/Burrows%E2%80%93Wheeler_transform)
* [Run-Length encoding](https://en.wikipedia.org/wiki/Run-length_encoding)

both implemented in Lua, with clean comments (hopefully) and tests.

I also brought some tiny changes (just reorganized some files) to my previous A-Star algorithm submission, for clarity. I'll be mirroring those changes to all the search algorithms I submitted further the A-star implementation.

Regards,
Roland.