Add support for passing optional parameters to register reader

[glopesdev]

This feature allows passing all optional parameters to register reader. The reader module was refactored so that all extra columns, e.g. type are included in the final frame after all conversion steps are applied.

For example, the below example retrieves the frame using UTC time and including the message type for all recorded messages:

from harp.io import REFERENCE_EPOCH
from harp.reader import create_reader

reader = create_reader('device.harp')
reader.WhoAmI.read(epoch=REFERENCE_EPOCH, keep_type=True)