Add sheet and file checks and prettification

[irm-codebase]

After all sections in a sheet are processed, there should be some standardized steps to run to ensure that the data is well formatted for the future.

Prettification includes:

• Convert 0 to NaN where applicable.
• Tidify the year columns into one.
• Ensure dtypes are correct (yearly data should always be numeric)
• Add mapping to convert strings that vary between versions (2-wheelers -> two-wheelers).

Checks should include:

• Validate that categories, technology types, subtypes and carriers do not deviate from a given range of strings. pandera should work well here.