Added NAV-TIMEUTC valid flag defines
Use NAV-PVT with ubx7 and ubx8 modules

This replaces NAV-SOL, NAV-POSLLH, NAV-VELNED and NAV-TIMEUTC.
Merge pull request #1113 from Kynos/gnss_nav_pvt

Use NAV-PVT with ubx7 and ubx8 modules