[Feature] Command prompt for zephyr log.

We would like to be able to executed zephyr shell commands directly from zephyr. 

I.e., in advanced settings, somewhere bellow the logging console, add an input field (simple text area? or does the console widget support something already?). 

After a command is entered, send it to UHK via the 0x1e usb command. It expects a c-style, null terminated string. 