Startcenter: use SCREEN_4_3 as default paper for presentations

Remove static to able to construct items with different
paper info.
Fix SCREEN_4_3 width and height values and use it for
presentations.

Change-Id: Ifba44675f6126ebfccf26f53f226214bed92352c
fdo#71628 Startcenter: remove thumbnail selection when focus is moved away

mnHighItemId is never assaigned with a valid value and there is
no sense to store one selected element's index anyway,
because there can be more.
The bMove parameter of ImplGetItem is never used and doesn' work
so remove it.

Change-Id: I91d6bc3fd13a2b44e6961fea66d02702a8f31c2b
Remove unused private member: pAccExec

Change-Id: Ie21f8a62213954da7f66c1fbe890ba9dee93cf77