SMM12 — Fix and improve CollectiveMeasurement examples

There are issues with some figures in the spec.
Figure 11.2, CollectiveMeasurement example, appears to assume the multiplicity of the "to" association from BaseNMeasureRelationship to DimensionalMeasurement is 0.*. It isn't. The multiplicity is 1.
The example needs 3 BaseNMeasureRelationships, one for each base DimensionalMeasurement.

In Figure 17.6 the accumulator field is missing. For clarity, accumulator=sum should be included. In addition, Figure 17.6 suggests to use one ObservedMeasure per each base Measurement, even when the Measure is the same. This suggests sub-optimal use of the spec and is, hence, misleading. The figure should suggest that the ObservedMeasure object can be shared.

In both figures, Figure 11.2, as well as Figure 17.6, the by already approved issue SMM12-149 introduced mapsTo relationship is not used, while these figures are the ideal cases to demonstrate its use.

And this immediately leads to one other, related, issue: Both figures, so, Figure 11.2 and Figure 17.6, demonstrate an important aspect of CollectiveMeasure. Namely: as long as the BaseMeasure can be shared, and as long as no in-lined rescaling parameters of BaseMeasureRelationship require any differentiation, the number of BaseMeasurements that is instantiated does not influence the definition of the BaseMeasure. Which is very important to foster re-use. So that, even while there are multiple BaseMeasurementRelationships, they may all correspond with and refer to one and the same BaseMeasureRelationship. The problem, however, is: though this is the intent of the spec, it is nowhere explicitly stated. And that is very confusing. We better fix that, by making that point very clear in the spec (the more so, as with BinaryMeasure(ment), the correspondence is never N - 1, but is always 1-1).

Update figures and add text for mapsTo

• Fix Figure 11.2 by adding 2 more BaseNMeasurementRelationship instance and moving 2 of the "to" associations from the original BaseNMeasurementRelationship instance to the new instances.
• Include mapsTo link in Figure 17.6
• Modify Figure 11.2 to have 2 base measures for collective measure. The first base measure maps to one base measurement in the collective measurement and the second base measure maps to 2 base measurements in the collective measurement. Make this clear by showing the mapsTo links.
• Add text in Semantics clause of 14.2 CollectiveMeasurement Class which clarifies that each BaseNMeasureRelationship instance there may be multiple BaseNMeasurementRelationship instances.