update nn_fn_standardize_data

[laurenbaggett]

minor modifications to fix errors when you're not training or classifying using all three parameters (spectra, ICI, waveform):

1. update function to only standardize variables that you're training/classifying on. added if statements to check trainTestSetInfo to see if variables are selected before standardizing. this fixes dimension errors within this function if you're not using all three parameters.
2. update output to ONLY include data related to variables that you're training/classifying on. created a dataOutput variable which is subsetted accordingly based on the parameters you've selected to use, rather than outputting a standardized version of dataInput as previously. this fixes dimension errors in the predict() function on line 123 of nn_fn_classify_bins if you're not using all three parameters.