Show file path instead of "(null)" when installing style via file open

And fix deprecation warning from passing an nsIFile

(Also updates the Zotero.Styles.install() documentation to note that the
first parameter's `file` property can be a string path.)

components/zotero-service.js

@@ -623,7 +623,7 @@ ZoteroCommandLineHandler.prototype = {
 						if(file.leafName.substr(-4).toLowerCase() === ".csl"
 								|| file.leafName.substr(-8).toLowerCase() === ".csl.txt") {
 							// Install CSL file
-							Zotero.Styles.install(file);
+							Zotero.Styles.install({ file: file.path }, file.path);
 						} else {
 							// Ask before importing
 							var checkState = {