Package configuration directory not used from Python installation

[djhoese]

User informed me of an issue that results from the configuration directory (etc) not being properly added to Satpy's list of configuration paths. The primary code that's the problem is here:

polar2grid/polar2grid/utils/config.py

Lines 33 to 37 in 6024d1d

	def get_polar2grid_etc():
	p2g_pkg_location = impr.files("polar2grid")
	if _is_editable_installation():
	return str(p2g_pkg_location / "etc")
	return p2g_pkg_location / "etc" / "polar2grid"

The final "polar2grid" in that directory is not accurate for conda/pure-python environments. The three cases that need to be handled are:

1. developer installation ("editable")
2. tarball installation
3. python (conda or regular) environment