[hybrisadaptor] Refactor sensor start/stop logic

Whether sensors should be started or stopped depends on a number
of state variables. Using case specific conditionals at places
where state variables might change makes the code fragile and
hard to maintain.

Separate sensor hal operations more clearly from logic and forms
dictated by sensorfwd conventions.

Use m_memberName naming convention for member variables, make
all member data private and usable only via accessor functions.

Use a single sensor start/stop policy evaluation function and
call it from each place where relevant state variables might
change.

Use sensorfwd specific logging functions instead of qDebug etc.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

adaptors/hybrisproximityadaptor/hybrisproximityadaptor.cpp

@@ -138,7 +138,7 @@ void HybrisProximityAdaptor::processSample(const sensors_event_t& data)
     ProximityData *d = buffer->nextSlot();
     d->timestamp_ = quint64(data.timestamp * .001);
     bool near = false;
-    if (data.distance < maxRange) {
+    if (data.distance < maxRange()) {
         near = true;
     }
     d->withinProximity_ = near;