for screenshots, use a resolution closer to the skins' minimum size

[ronso0]

from #126 :
I think we should take the screenshots with a resolution close to that each skin was designed for. Like, when the minimum size is 1024px we can take a screenshot with either 1024px or 1280px.
(temporarily changing the minimum size to the desired resolution instead of manually resizing the window..)

reason:
Looking at the Shade screenshots taken with [FullHD x N] will raise some questions about the layout:
why is there so much whitespace in the decks? why is there an extra row for the hotcues? why is so much space wasted for the library cover art? ...

Shade / Deere / Tango: 1280px
LateNight: 1600px

what do you think?