add WARegistry>>handlers? (and WAApplication>>sessions?)

[GoogleCodeExporter]

Inspired by this code posted on the mailing list:

(WASession allSubInstances select:
    [ :ea | ea isActive & (ea application name = 'yourApp' ) ]) size

I wonder whether we should add #handlers or #handlersDo: or something to
WARegistry. You can, of course, get that indirectly in 2.9 by accessing
#cache directly but that's a bit obtuse and it might be better if most
people didn't have to rely on accessing the cache unless they were
specifically trying to configure it. That keeps the fact that WARegistry is
implemented using WACache more hidden.

Perhaps we'd also want to add #sessions to WAApplication, which would just
call #handlers... might be intuitive for people and a good public API to have.

Obviously these methods would all need to return a copied array (if WACache
doesn't already) to make sure they werne't modifying internal collections
of the cache.

Original issue reported on code.google.com by jfitz...@gmail.com on 27 Jul 2009 at 2:15