some fixes to icon background
Merge branch 'icons' of https://github.com/qreal/qreal into trikDemos

Conflicts:
	plugins/robots/editor/images/iconset1/images/ledBlock.svg
	plugins/robots/editor/images/iconset1/images/loopBlock.svg
	plugins/robots/editor/images/iconset1/images/waitForLightBlock.svg
advanced cache for big svg images
Merge branch 'trikDemos' of https://github.com/qreal/qreal into trikDemos