RangeFinder: TYPE param description to PX4-I2C
AP_NavEKF : Fix bug in reset of GPS glitch offset

The GPS glitch offset was being zeroed during position resets. This caused the filter to reject subsequent GPS measurements if the GPS error persisted long enough to invoke a timeout and a position reset.
Copter: use define for pre-arm compass offset check
AP_GPS: Adding support for the NEO7 GPS
Merge remote-tracking branch 'ardupilot/master'