driver simsem: allow to select the simulation image
install: improve simulated secom

longer default dwell time (to avoid too high CPU usage by default)
faster drift (to make it more fun)
driver simsem: add fake focus

the further away from the original image, the more blurry is the image
config: add ebeam focus to secom simulators
cli: display metadata with list-prop

Handy to analyse some hardware when the backend changes the metadata
Also fix the display of events and dataflows in machine mode
Also display the speed range of the axes