ZK JSON: improve usability by accepting Collection instead of List

the classes JSONValue and JSONArray could accept java.util.Collection instead of just List, this would improve usability of those classes. The change would only change one interface and have little impact on the implementation in JSONValue
the same improvements were suggested and accepted in json-simple, but were never released...
see https://code.google.com/p/json-simple/issues/list?can=2&q=Collection

attached the 2 patched files...