Add ID:s

[redhog]

• Hash of original lines
• Hash of nmea line contents (without tagblock etc)
• Random id for differentiating copies of the same line

[schwehr]

@redhog suggested https://docs.python.org/2/library/uuid.html for the random id.

[redhog]

Possibly shortened by using a base64 rather than hex encoding:

import uuid, base64
msg_id = base64.b64encode(uuid.uuid4().bytes)

We can't just use the raw bytes, as e.g. the json container does not support that.