Many improvements

* 'optipng' every png (reduce size) (**new dependency**)
* Apple icons' names are generated by this template:
apple-touch-icon-SIZExSIZE-precomposed.png
* favicon.ico includes 24x24 and 64x64 versions
* .png, which are necessary only to generate favicon.ico are deleted
* Added 195x195 png for Opera Speed Dial
* Included test image
* Changed html helper output (added Opera Speed Dial support, better
apple-touch-icon support)