Fix #supply_status to be shown

Outdated Font Awesome class names were still used.  They should be
updated in 46a4fb8221e206ec7244da9860c141168696af99.
Change the icon to notice fallback supply

It might be confusing to use the same icons for both #offline_mode and
#supply_status.
Show nothing for successfuly generated supply
Use meaningful class name for #supply_status
Merge branch 'fix-supply-status-notification'

Close gh-107.