DIP54 : revamp of Phobos tuple types

[Dicebot]

http://wiki.dlang.org/DIP54

This is follow-up of several hot discussion threads that have 
happened several months ago. It has become pretty clear that 
there is no good way out of existing situation and least bad 
needs to be picked just to move forward (because it still be 
better than current horrible one)

Linked proposal was discussed in short e-mail conversation with 
Andrei (with silent observation with Walter) and is mostly 
pre-approved. I am interested in general opinion of community and 
suggestions for any smaller tweaks before starting to work on 
pull requests.

Thanks for your attention.