Both of these support a number of features not available in hail.plot:
- interactive legend (click to hide/show elements)
- labelling with continuous expressions
- labelling using multiple expressions (will display a dropdown selection widget)
- specifying color schemes
- hovering on points displays their coordinates, labels and additional source fields
- legend is also displayed outside of the plotting space to be unobtrusive

* Renamed fields to be as close as possible to previous scatter plot names
* Added marker size option

Removed unused import +  space from experimental/plots

* Small join_plot change: assign gray color to missing factors in provided color palette rather than throwing an error

fixed import

fixed scatter header

- `source_fields` -> `hover_fields` (clearer, same as `manhattan`)
- removed `collect_all`, use `n_divisions is None` instead
- Set `n_divisions` to previous default value of 500 everywhere

* small fixes, cleaning ups

* Fixed an issue with non-numeric, non-string types for hover fields

* Also corrected indentation of scatter doc