Slow command execution when using Telnet on AVC-A10H

[henrikwidlund]

I've noticed that whenever I execute a command that doesn't use skip_confirmation=True each command takes 3 seconds. Using HTTP doesn't have this problem, and I'm wondering what the best approach to fix this would be (I'd like to provide a PR to fix it).

I've been thinking of two solutions:

1. Property skip_confirmation in DenonAVRTelnetApi with default value False
2. Expose the skip_confirmation flag on all commands with default value False
3. Expose flag to force use HTTP even when Telnet is available

Option 1 is probably easiest to use, but doesn't give any granular control, and might cause issues with the existing overload on the send command methods. Option 3 feels unintuitive.