Added support for proprietary u-blox messages

I have added support for u-blox proprietary Messages for:
- Lat/Long Position Data (PUBX00)
- Satellite Status (PUBX03)
- Time of Day and Clock Information (PUBX03)

for PUBX03 the individual satellite status is not parsed but given back as a list (satellite_status).

Also I have added support for TXT NMEA messages.