Add \since tag to QtSensor classes.

QtSensors was released first by Qt 5.1.

A few whitespace changes go along as well to unify the formatting.

Change-Id: I6f6e15c95c1a5f33731782e429e87cef68e96e3b
Task-number: QTBUG-36775
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Doc: Applied title case in section1 titles

Task-number: QTBUG-41250
Change-Id: I788332e3db66e8188fc7d64d1e31995f4b432932
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Merge remote-tracking branch 'origin/5.4' into dev

Change-Id: Ie542c953df0bac854da2fd2f00043509addf87f2