Enhancement to Web UI client settings

If there is no image for a specific client model, the default image is
displayed.

Source of the image is: GitHub squeezeplay
icon_default.png  renamed to default.png (according to the syntax of the other images)

+ two additional images for new models
OpenFrame1.png
OpenFrame2.png

What's 'baseSkin' supposed to do? Shouldn't this be 'EN'? And shouldn't we check for  skinOverride first instead? Most likely it doesn't matter anyway, but it would be correct. 'skinOverride' would be the skin you can chose in the URL when opening the web UI. Eg. http://localhost:900/Classic/ -> skinOverride = 'Classic'. 'EN' is the base skin.

And we don't need to check for default.png, as we know we do commit it.