backends-switch: add colors

With css, a red dot for non-responding backends, a green one for
those which work
fix: remove print
backends-switch: add colors

With css, a red dot for non-responding backends, a green one for
those which work
fix: remove print
Merge branch 'feature-backends-switch-colors' of github.com:matthieucan/adagios into feature-backends-switch-colors
replace circles to use the same as in the hosts list
Merge pull request #367 from matthieucan/feature-backends-switch-colors

backends-switch: add colors