ADD: Ka-SACR Investigation - Column Extraction from RHI scans

[jrobrien91]

• adds bnf-sacr-rhi.ipynb notebook that investigates column extraction for PPI and RHI scans
• adds a split_column function to the standard RadCLss methodology for RHI scans.
  • as RHI scans will generate non-unique values for height, users cannot concatenate across the day
  • splits each RHI column into four unique DataSets, then concatenates on time