[icu-design] Raising methods into Collator

[Mark D. <mar...@ic...>]

Right now it is a bit clumsy for people to use some very common (and needed)
options with collators. That's because the necessary methods are not
available without casting.

 RuleBasedCollator mainCollator = (RuleBasedCollator)
Collator.getInstance(locale);

 mainCollator.setAlternateHandlingShifted(true);

 mainCollator.setNumericCollation(true);


I propose that we move these methods up into the Collator class, so that
this is not necessary. The semantics will be that they set the particular
behavior whenever available in the subclass.

Mark