SMM12 — Add support for Scale of Measurement

Scales of Measurement are a fundamental property of a Measure describing the allowable mathematical transformations that can be legitimately applied to it.
Attached are some URLs that will give you an overview of Scales of Measurement. Since they therefore determine the statistical methods that can be applied to the Measure, they need to be treated as a first level attribute of a Measure.
http://www.math.sfu.ca/~cschwarz/Stat-301/Handouts/node5.html
http://en.wikipedia.org/wiki/Scale_of_measurement (not always written in easily understood terms)
http://www.wadsworth.com/psychology_d/templates/student_resources/workshops/stat_workshp/scale/scale_01.html (tutorial - behavioral science view)
It is proposed to introduce an Enumeration to define the possible Scales of Measurement: ordinal, nominal, interval and ratio. Also to add an attribute to Measure, to define its scale.

Scale of Measurement was implemented already

Scale of Measurement has already been implemented in SMM 1.1.