[branch 1.2] Transparent and truly vectorial embedded SVG

Context: branch rev. 5327

Current branch support has a couple of limitations:

*) transparency of the original image is not preserved
*) images are rasterized when embedded and not scaled anymore.

This affects screen display, printing and PDF generation.

This patch corrects these two issues; it is is actually a port of the recent changes to trunk SVG support (without the ImageStore machinery, of course). As for trunk, it no longer uses the Image cache buffer and goes through Qt own SVG rendering.

I have tested it on a few scores, on screen and with generated PDF (as PDF generation uses printing, I assume it works also for 'real' printing).

M.