use 9.80665 as standard gravity for calculations.

Task-number: QTBUG-32751

Change-Id: I65076fa41d5c6a4e716df96bc5156068c1bd0040
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
add gyroscope for sensorfw backend

Task-number: QTBUG-32754

Change-Id: I9037c20953d67584fdfeb4d0fabdfd73f919f14c
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>