plugin manager: allow pluginInfo import to have relative URL to an imported plugin in it's own directories or secondarily relative to the executing arelle's plugin directory
plugin manager: allow pluginInfo import to have relative
URL to an imported plugin in it's own directories or
secondarily relative to the executing arelle's plugin directory

sternshus/Arelle,sternshus/Arelle,sternshus/Arelle,sternshus/Arelle,sternshus/Arelle