Add some model tests, other minor clean ups.

* Add model_tests, which tests beam, doublebeam, and numberCountsKnotsSpline.
  numberCountsDoubleLogNormal should be added later.
* A bunch of formatting fixes.
* Regroup some of the tests in initFile_test and specFile_test.
* beam/doublebeam return 0 size for components without any pixels rather
  than NaN.