add Reader power configuration to settings

[truedat101]

• find out default reader antenna power setting
• display this in the settings as an editable field
• make it editable to change the gyr_values.yaml

[truedat101]

Requested by @tagstand2 .

[truedat101]

It looks like there is a way to set the antenna power. I'll dig up the details in the api.

[truedat101]

We can set this on startup with an RA<#> command. Look into how to send.