Create a conversion flow of the icon set

[krzysztofspilka]

We need to extend the current setup to maximize the potential of our SVG icon set. Specifically, each time we add a new icon, the following sequence should be run:

1. Create an optimized SVG version of the icon,
2. Create a PNG version of the icon,
3. Create a larger PNG version of the icon (2x - for Retina screens),
4. Create a symbol sprite from SVGs,
5. Create an icon font from SVGs,
6. Add the new icon to the list of Sass generator,
7. Add the new icon to the list of Less generator.

Also, our documentation at handsontable.com/docs should generate the list of icons automatically.