Misc improvements to dashboard.php and dashboard_eth0.php:
They use new functions from the newest raspap release, which decreases redundant code.
The name of the interface (eth0 or wlan0) is only in index.php, not in multiple places in the dashboard files, making it easier if the interface names ever change.
The Wi-Fi link quality output is improved and more accurate.
Misc improvements to dashboard.php and dashboard_eth0.php: