Clean up echoed firmware lines, connect info.

Presently, when you connect to a printer using pronsole, one sees something like:

```
uninitialized>start
uninitialized>Printer is now online
uninitialized>echo: External Reset
printer>Marlin 1.0.0 RC2
...
```

With a few carriage returns and some string hackery, we clean up
the output so that one sees:

```
No port specified - connecting to /dev/ttyACM0 at 115200bps
start
Printer is now online
External Reset
Marlin 1.0.0 RC2
```

Much cleaner!