Add a tool button showing a dialog with file name
and size for exporting images from SVG.
[ChangeLog][ImageViewer] Added option to export images from SVG.
Change-Id: I84e04dc166e70b0359eba0f19703a75b882a2bc2
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@theqtcompany.com>
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>