TLS and Insecure can be set per device in config yaml

[klaper]

• Adds port (default 8728) setting to device setting in config file
• Adds tls (default: false) option to device settings in config file
• Adds insecure (default: false) option to device settings in config file
• Moves tls and insecure connection options settings from collector to device, allowing to have mixed connections for devices in yaml config file
• updates README.md

[nshttpd]

Thanks @klaper. I like this PR in practice, but how bad will it break all the existing configs out there in the wild?

[klaper]

Before there was no possibility to set port or TLS. Since all added settings are optional with defaults set to same values as before, this change should have no effect on any of current configs (including those provided with command line).

[klaper]

@nshttpd any news :)