Crash: export of a big alignment to SVG

1. Open "ftp://ugene-quad-ubuntu/misc/UGENE-4299/Chikungunya E1.fasta".
2. Zoom out once.
3. Export full image to SVG.
=> UGENE crashes.

Add the restriction for exporting of alignment images to SVG: if lines*alignment_length > 400000 then prohibit the export.
400000 alignment characters => ~200 Mb of an SVG file. It is really big picture and it is hard to open in an image viewer.