Add support for different Earth radii approximations into LayeredSphericalAtmosphereBuilder

See merge request !209

finally save test-output as artiface for coverage job

See merge request !228

fix corsika-data

See merge request !227

cache the corsika-data, too

See merge request !218

Ci again

See merge request !217

Resolve "ShowerAxis mixes signed and unsigned int in comparison"

Closes #277

See merge request !215

faster dev build

See merge request !216

use of rules

See merge request !214

Resolve "Runtime error with pythia"

Closes #225

See merge request !191

Initial refractive index interface and constant refractive index model.

See merge request !212