In cxxtest, TS_ASSERT_DIFFERS(a, b) tests !(a == b) and not (a != b).
Therefore, to test a::operator!=(b), we must avoid TS_ASSERT_DIFFERS()
(that will test !a::operator==(b)) and write instead TS_ASSERT(a != b).
Delete class CalibrationMeasurement and add class CalibrationRequest:
the ReferencePoint must be linked by the Request, not by each
Measurement of the Request.
Adapt ReferencePoint to link a CalibrationRequest instead of a
CalibrationMeasurement.
Request:
- Destructor is now virtual to allow polymorphism.
- Reactivate tests on get_measurements() and set_measurements().