Better Error handling for file parsing

Q: Do some type of check that X amount of CCNC data "matches" with SMPS data? [i.e. ensure that all CCNC files have been selected]

File: Controller.py Function: parse_files - approximately line 162

Currently, no error handling if wrong file types or only one file type is selected.

• Only txt selected
• Only CSV selected
• Not enough CSV's selected (Currently raises ValueError when applying savgol_filter
• Only proccesses first text file regardless

helper_functions.process_csv_files

• Error caught but not handled

Related to #40