Cleaned up unnecessary i18n strings

Others that should be considered for removal:
* gnl-close (same text as "close" in core i18n)
* gnl-main-page (same text as "main-page" in core i18n, although in core "page" is not capitalized)
* tmpl-settings (same text as "settings" in core i18n)
* tmpl-toppage (same text as "tphp" in core i18n, although in core "page" is not capitalized. note includes should be updated if removed)
* tmpl-share-page (doesn't seem to be used)
* dlg-close (doesn't seem to be used)