Encode measure comparator values in spek

[grosscol]

In order to correctly generate feedback figures with comparators with non-static values, e.g. achievable benchmark or peer mean, the templates need to be able to read the value at runtime.

Having the calculation re-done again in the template is inefficient. It would also require handling the annotations again.

Devise method by which the comparator values of the measures in the spek will be recorded in addition to the annotations of the performers. This will also enhance the audit trail as it answers the question of, "what was the value of the comparator when the analysis was run?"