#allow shareddata add!/put!/remove!/clear! to take
#a collection name or collection as a first arg
fix up issue [#26]
Minor fixes to named shareddata lookup.

With the prior implementation, it was possible for add! and put! to
attempt to add or put on the wrong type of object. Also, specifying
any collection name that wasn't empty an empty collection would
trigger the ambiguous exception.
Document shareddata changes.