U-blox driver rework, step 1

Handle u-blox 7+8 GNSS, too.
Disabled NAV-SVINFO for now (will be rewritten as an optional feature in
a later step).
Reduced parser buffer size from 300 to 80.
Beautifications for tab size 8

Beautifications for tab size 8
U-blox driver rework, step 2

Moved satellite info from vehicle_gps_position_s into a new uORB topic
satellite_info.
Renamed satellites_visible to satellites_used to reflect true content.
sdlog2 will log info for GPS satellites only for now.
U-blox driver rework, step 3

More sat info isolation
Flush input after changing baudrate to allow driver restart w/o GNSS
module restart
Merged ubx driver part of pull request #1031
Initialize rate values

Initialize rate values (else invalid rates wil be displayed during the
first measurement interval).
Gps driver: make enable_sat_info a command line option
U-blox driver rework,, step 4

Config phase and parser rewrite
Remove unreferenced SVINFO length defines
Merge master with the exception of ubx.cpp and ubx.h
Merge sAcc & pAcc scaling fix from branch inav_gps_delay
Request and display MON-VER message at startup
Store hash instead of full strings for SW & HW version
Define NAV-PVT message
Merged upstream master into gnss_rework branch
Merged upstream master, add missing change
Fix sdlog2 GPS time copy for log_on_start situation
Merged master to gnss_rework
Merge pull request #1108 from PX4/gnss_rework

Gnss rework