fix: custom bounds and p0 will be ignored if fitting is triggered by property getters.

[fncokg]

In the current code, the custom bounds and p0 stored in self._kwargs are only used when self.fit() is called in __init__():

scikit-gstat/skgstat/Variogram.py

Lines 392 to 394 in 46bc79e

	fit_bounds = self._kwargs.get('fit_bounds') # returns None if empty
	fit_p0 = self._kwargs.get('fit_p0')
	self.fit(force=True, bounds=fit_bounds, p0=fit_p0)

But not in some property getters, for example in transform():

scikit-gstat/skgstat/Variogram.py

Lines 1809 to 1810 in 46bc79e

	if self.cof is None:
	self.fit(force=True)

or in describe():

scikit-gstat/skgstat/Variogram.py

Lines 2611 to 2612 in 46bc79e

	if self.cof is None:
	self.fit(force=True)

etc.

Considering this, I suggest getting custom bounds and p0 within fit().