Assignment datasets

[fcorowe]

Decided that each assignment will be a compilation of micro-assignments based on each block. That way, the person responsible for each block prepares questions based on data that are different than those used in the chapter, but that can be recycled across the micro-assignments for different chapters.

Assignment datasets will include:

1. AirBnb for Paris: Points, Spatial Econometrics - @darribas
2. Census for area other than Liverpool (Introduction, MLM, GWR, Space-Time Analysis) - @fcorowe
3. Alternative flows (provided by @fcorowe, prepared by @darribas)