parabola sTGC positon reconstruction
Alternative to the weighted average position reconstruction for sTGC clusters: Find the peak of the cluster with a parabola defined by the strip with the largest charge and its left and right neighbor. Apply a non-linear correction function to obtain the cluster position. Returns a result in all cases, no optional failure. Error conditions are encoded in PARABOLA_FLAGS, but not returned (yet). As a work-around, the flags are multiplied by 20 microns and added to the error estimate, but only for problem clusters. The position of the strip with the largest charge is returned in case of errors. Parameters positionResolution and angularResolution enter in the estimate of the error on the mean position.