Code Optimization: input data + parsing

[avouros]

The part of the code that reads CSV or XLSX files and parses the info of interest is running too slow, especially when we have XLSX files.
Segmentation: load_data.m --> parse_data.m --> read_ethovision.m / read_ethovision_xlsx.

Note: for reading XLSX files the command xlsread is being used (xlsread-ref)