Update designator draft proposal.

Mention more extant implementations. Add inspirations for new material.
Redo completely the items before 8.5.1/2. Remove the text after
8.5.1/2.  Update 8.5.1/2 and /4. Add updates to 8.5.1/6 and /12 and
add text in between them. Remove 8.5.1/5, /7, /8 (maybe), /9, /10,
/11, /15, and /16. Add updates to 8.5.4/4 and 14.5.3/4.
Update array draft version 2 proposal.

Change reference to the Standard from N3691 to N3797. Update the label
numbers of section [meta] moving from 20.11 to 20.10. Correct template
header to std::array::size. Add N3526 as a reference. Do some tweaks.
Add two type-traits proposals.

Split the array-oriented traits from N3794 to a new proposal. Add a
proposal for type transformations that are described in the Standard
but do not have a type-traits class.