Improved handling of corsika.Library

Closes #718 (closed)

This update handles "unknown" directories by simply skipping them instead of throwing an error. For example,

In [2]: lib = corsika.Library("test_dir")
[WARNING] - corsika - Could not find a configuration file in test_dir/interaction_hist. Skipping sub-directory
[WARNING] - corsika - An error occured loading a RadioProcess: single positional indexer is out-of-bounds
[WARNING] - corsika - Unable to instantiate an instance of 'RadioProcess' for a process called 'CoREAS'. Skipping 'CoREAS'
[WARNING] - corsika - 'RadioProcess' object has no attribute '_RadioProcess__data'
[WARNING] - corsika - An error occured loading a RadioProcess: single positional indexer is out-of-bounds
[WARNING] - corsika - Unable to instantiate an instance of 'RadioProcess' for a process called 'ZHS'. Skipping 'ZHS'
[WARNING] - corsika - 'RadioProcess' object has no attribute '_RadioProcess__data'

applications/c8_air_shower.cpp

@@ -189,7 +189,7 @@ int main(int argc, char** argv) {
       ->group("Config");
   app.add_option("--hadcut", "Min. kin. energy of hadrons in tracking (GeV)")
       ->default_val(0.3)
-      ->check(CLI::Range(0.000001, 1.e13))
+      ->check(CLI::Range(0.02, 1.e13))
       ->group("Config");
   app.add_option("--mucut", "Min. kin. energy of muons in tracking (GeV)")
       ->default_val(0.3)