Remove generate_luc_layer.py

[mdales]

Early on we implemented a script to make a LUC layer that covered just the project + boundary area, assembling the data from the individual JRC tiles as necessary.

Since then yirgacheffe has implemented a GroupLayer, which mostly makes this script somewhat redundent. To simplify the code here we should probably switched to using GroupLayer (already in use in newer sections of the pipeline) everywhere and remove this script.

[mdales]

This is addressed in #113