upgrade to prototype.js 1.6.0.2

the current version of prototype.js including in nxthemes-jsf is 1.6_rc0. The latest available version is 1.6.0.2 which includes bug fixes and a security fix.

see http://www.prototypejs.org/2007/10/16/prototype-1-6-0-rc1-changes-to-the-class-and-event-apis-hash-rewrite-and-bug-fixes

the upgrade requires that the access to hash objects be rewritten. The latest version of scriptaculous (1.8.1) will have to be used too.