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.)

chrome/content/zotero/xpcom/style.js

@@ -269,10 +269,11 @@ Zotero.Styles = new function() {
 	/**
 	 * Installs a style file, getting the contents of an nsIFile and showing appropriate
 	 * error messages
-	 * @param {Object} style An object with one of the following properties
-	 * 		- file: An nsIFile representing a style on disk
-	 * 		- url: A url of the location of the style (local or remote)
-	 * 		- string: A string containing the style data
+	 * @param {Object} style - An object with one of the following properties
+	 *      - file: An nsIFile or string path representing a style on disk
+	 *      - path: A string path
+	 *      - url: A url of the location of the style (local or remote)
+	 *      - string: A string containing the style data
 	 * @param {String} origin The origin of the style, either a filename or URL, to be
 	 *     displayed in dialogs referencing the style
 	 * @param {Boolean} [silent=false] Skip prompts

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 = {