Changes to ansi2decho

These changes include: 
- bold/light 8however you wish to call it) tags and colours
- support of the lower 16 byte in the third argument of xterm256 colour indexed commands
- use rex to matc the complete ANSI pattern. The lua pattern metod could lead to false positives.

I currently plan to write unittests for the ansi2decho method, so more commits are about to be part of this PR.

I also used this method in my lua setup and played with the Achaean xterm256 support.
Done. See 1cc602c9584d56c04e0cd37a0df17c878728d1e5