Improve specification of string ordered comparisons

The current spec defines string comparison using one of the operators <, <=, >, or >= in terms of when one string is less than another. That's fine for <, but:

for <= it effectively assumes issue 245 is fixed (i.e. that a <= b for strings a and b if a < b or a == b)
for > and >= it leaves quite a lot to the reader's imagination.

Once we've settled on issue 245, the above should be addressed.

~We should also adopt a similar approach for ordered comparisons (<, >) of arrays if issue 244 is adopted.~ (It wasn't.)

(I labelled this issue as editorial because I don't believe it will change the intended semantics in either case.)

ietf-wg-jsonpath / draft-ietf-jsonpath-base

Improve specification of string ordered comparisons #249