Add wake on LAN option to wake up the host systen

[chriss158]

Hi Thomas,

Thanks for the great addon.

My backup system does not run 24/7, so I was missing the option to wake up my system before copying the backup.
This PR adds the option to do a WOL before copying the backup to the host system.

A few notes on implementation:

• If WOL is enabled and host_mac is missing, the addon will fail on startup because the addon is misconfigured.
• When the addon pings a DNS name, the ping output may be "ping: bad address". This seems to be a DNS issue. So I added a log message to indicate that the user should use the IP address instead.

The process of doing a WOL is as follows:

1. Check if WOL is enabled

2. Check if host is online

   • If the host is online

     1. Continue copying the backup

   • If host is offline

     1. Send WOL

     2. Ping host system 100 times

     3. Check if host comes up within 100 pings

        • Host comes up within 100 pings

          1. Wait another 60 seconds for the host to settle.
          2. Continue copying the backup

        • Host did NOT come up after 100 pings

          1. Cancel the backup copy with a warning

Thanks for reviewing my PR and just let me know if there is anything to change.

[thomasmauerer]

Thanks for your two PRs. I'll take a look at them on the weekend.