Perform basic data cleaning and handle missing values

[fusr]

• missing values, imputation?
• joining tables
• what columns to drop
• get external data (weather & tyre data)
• what tables to drop
• test/train split

-> granularity?! weather data is hourly, tyre data based on laps. How to deal with this?! Take avrg. hourly data, or break it (for the first iteration) down to two categories: dry / wet. Because hourly data is too inaccurate anyways. (possibly more accuracy for future work?)