Fix all compiler errors from the merge

src/descriptor_identifier/Model/ModelClassifier.cpp

src/descriptor_identifier/Model/ModelRegressor.cpp

src/descriptor_identifier/SISSO_DI/SISSOClassifier.cpp

src/descriptor_identifier/SISSO_DI/SISSORegressor.cpp

src/feature_creation/feature_space/FeatureSpace.hpp

src/feature_creation/node/ModelNode.cpp

src/inputs/InputParser.cpp