[TIMOB-19186] Windows: Optimize Titanium::getAppInfo()

Currently Titanium::getAppInfo attempts to load _app_info_.json even if previous attempts failed to load it, because it didn't exist.

Christopher Williams 2015-07-07

It also loads it multiple times, once per property, rather than just reusing the parsed json.

Gary Mathews 2015-07-07

It shouldn't

   // Load _app_info_.json
   if (json.IsUndefined()) { // this should stop that happening?
   	json = loadJson(get_context().get_global_object());