Update SkyBrightnessCoefficients.mo

Corrected typo in the definition of the sky brightness coefficients
Merge pull request #153 from open-ideas/issue127_UnitTestCoverage

This is still work in progress but I have merged these changes so far
accepted changed reference results from Annex60 models for easier work flow
fixed unit test files for BesTest
accepted initial versions of solutions for bestest
Merge branch 'Annex60' into issue127_UnitTestCoverage
changed reference results of BesTest according to bugfix in sky brightness calculation