move background view to the right directory
rename joinPaths to join in Paths file
use dahufile URL protocol
create workspace's screen view
setup click event on filmstrip screens'
display workspace view
update workspace view onPictureSelect event
capture and handle model change
cleanup

- delete unnecessary dependencies
- remove useless debug log
change event namespace and rename event
skip rendering of non-background object
reset stylesheet
initial dahuapp stylesheet
clean dahuapp main layout and add toolbar