Automates storing data as a JSON object. Example:

var cache = new DataCache('linked-urls');
cache.setValue('moo', 'http://google.com');
var moo = cache.getValue('moo', 'DEFAULT');
// --------------------------------------------------------------------------
GM_registerMenuCommand('Edit cache', function() {
cache.edit();
}, 'p');

Requires both GM_getValue and GM_setValue permissions to be granted to any user script that requires it.