Uncheck clear all in clear cache function

As far as i understand i delete all screenshots and settings and and and when simply clicking the clear selected a littel bit to fast not reading all the checkmarks. So i would suggest for a more risk free usability to change it so that you have no checkbox selected and can select them all by a button or link click. So it would also be more easy to select just one or two items then removing all the ticks that you don't want.
Thanks folks for the great application!

Carsten