Add quality to individual formats

[svenruegg]

To make the individual formats more flexible I wanted to add the quality setting there as well. With that the 'large' format can have a different quality setting the 'small' f.ex

The format quality setting will override the global one. If no quality is set on the individual format, the global set quality is used.

[svenruegg]

@nicolashmln any update on when this will be reviewed?