Introduce test-stressgraphics-svg test with reference files

First provide SVG mode in stressGraphics to let generate only SVG files.
Such SVG created in compact form which is now provided with TSVG class.
When check reference files, compare line by line and print difference
Some canvases disabled because of huge size which should be optimized first

Content of reference SVG files must be exactly the same on all platforms.

Author: linev