Provide means to access raw serial interface

[jmpinit]

The client application will then be able to easily access the comm data for debugging, so we can remove:

ebb-control/src/serial.js

Line 43 in 60b7e18

console.log('rx:', line);

and

ebb-control/src/serial.js

Line 71 in 60b7e18

console.log('tx:', str);