Complete the signature of plot methods with all their kind options

[maximlt]

The converter class has a mapping from plot method name to options _kind_options.

class HoloViewsConverter:
    ...
    # Options specific to a particular plot type
    _kind_options = {
        ...
        'hexbin': ['C', 'reduce_function', 'gridsize', 'logz', 'min_count'],
        ...
    }

These options do not all appear in the signature of the plot method exposed to users, for instance, min_count for .hexbin().

class hvPlotTabular(hvPlotBase):
    ...
    def hexbin(self, x=None, y=None, C=None, colorbar=True, **kwds):
        ...

I'm not sure why some options aren't exposed in the signature, if there's one, I haven't found it yet.

Otherwise, I'd suggest adding:

• making sure the options already defined in the signature are correctly documented in the docstring
• add all the options not defined in the signature but in _kind_options to the signature.

In order to complete the second item, the default value of these options will have to be found and exposed. I assume they map to some HoloViews Parameter.