Add some knot position getters to numberCountsDoubleLogNormal, add unit tests.

* Add getKnotPosition, getSigmaPosition, getOffsetPosition methods
  to numberCountsDoubleLogNormal
* Add unit tests of numberCountsDoubleLogNormal for
  ** more constructors
  ** setting positions
  ** setting and getting parameters
  ** Number counts, total number of sources, R.
* Add unit test for array numberCountsKnotsSpline::getR