fix #13: Error with Sightly Export/Import when opened file not in jcr_root
fix #13: Error with Sightly Export/Import when opened file not in jcr_root

* improved Preferences module in order to always specify the context for the used settings

Adobe-Marketing-Cloud/aem-sightly-brackets-extension,Adobe-Marketing-Cloud/aem-sightly-brackets-extension,justinedelson/aem-sightly-brackets-extension,justinedelson/aem-sightly-brackets-extension,justinedelson/aem-sightly-brackets-extension,Adobe-Marketing-Cloud/aem-sightly-brackets-extension,cpilsworth/aem-sightly-brackets-extension,cpilsworth/aem-sightly-brackets-extension,cpilsworth/aem-sightly-brackets-extension