Use array for list values in scriptable
Added "pack()" scriptable function
Added "setitem()" and "getitem()" scriptable function

Command "getitem()" retrieves item at given index as object with
properties MIME->DATA (same as "unpack()").

Command "setitem()" creates (at given index) item from given object.
Fix running command from action dialog
Faster item insertion and removal through script
Focus next item if removing current