API for built-in JSON object
fixes LIBS-57
Several Ext AS get methods claim to return void
http://jangaroo.myjetbrains.com/youtrack/issue/LIBS-57

Found out appropriate types for most get...() methods that used to return void.
On the fly, added "private" method ext.form.ComboBox#restrictHeight().
fixes LIBS-58
Support window.localStorage and window.sessionStorage
http://jangaroo.myjetbrains.com/youtrack/issue/LIBS-58