Support logging 'unknown' OEM7 messages under Oem7Raw topic

Populate gps_common/GPSStatus.status with more detailed status info

Source gps_common/GPSFix, gps_common/NavSatFix position data from the most recent and higher quality INSPVAS or BESTPOS/BESTVEL messsage.

Previously, position data was always sourced from BESTPOS/BESTVEL, which is transmitted at lower rate than INSPVAS (#13)

Support nmea_msgs/Sentence for all OEM7 NMEA0183 messages (#4)

Support nav_msgs/Odometry, with position and orientation populated based on BESTPOS/BESTVEL/INSPVAS (#8)

No feature changes

Build fixes and documentation improvements.