Add data and generation scripts for irregular shapes (fixes #98)

[Rekyt]

This PR aims to add irregular shapes for sites and provide ways of aggregating data on them.

It aims to tackle #98 and #123

[Rekyt]

This PR still has to edit the upscaling vignette to adapt to the new aggregation function

[ahasverus]

Thanks for this huge work.

Just a question: I don't know if agg_grid (parameter name) is still appropriate now we can handle different input types (raster, polygons, etc.).

[Rekyt]

Sure! I fell the same, what would be a good name?
aggregation_object seems to long
Something with "upscale" in the name? With "object"?

Could be transformed to agg_geom for aggregation geometry? Or target_geom for target geometry?
What do you think?

[ahasverus]

Sure! I fell the same, what would be a good name? aggregation_object seems to long Something with "upscale" in the name? With "object"?

Could be transformed to agg_geom for aggregation geometry? Or target_geom for target geometry? What do you think?

I like agg_geom.

[ahasverus]

Or maybe new_geom?