tools/upload_file.py: implement getline()

[josuah]

This should make the I/O handling a lot easier, allowing to read data back from the Monocle.

This turns the data from Bluetooth, segmented into packets received asynchronously (low-level interface) into a stream that can be read using getline() (with a custom delimiter possible).

This makes it a lot more convenient to build scripts for the Monocle.
This could be turned into a Monocle library that connects to a Monocle:

monocle = Monocle(mac="monocle_mac_address_here")
monocle.send_command("print('abcd')")
assert monocle.getline(delim="\r\n\x04") == "abcd"

[josuah]

The current implementation does not go that far though. A bit of polishing, but the mechanism is there.

[josuah]

The output is also a bit more pleasant now:

$ python ../tools/upload_file.py color.py
uuids=['6e400001-b5a3-f393-e0a9-e50e24dcca9e']
Connected to the Monocle
>>> opening a file to write to
>>> writing the data to the file
.........................
>>> closing the file
>>> script done

Device was disconnected.
$

[josuah]

The usability and output got improved even a bit more:

$ python3 ../tools/upload_file.py *.py
uploading color.py ......................... done
uploading display.py .................... done
uploading font.py ........................................... done
uploading glyph.py ............................. done
uploading sprite.py .................................... done
uploading text.py .................................. done
uploading vector.py ................................................. done
$