Rename electron-mattermost to Mattermost at implementation

npm package name (package.json: name) is "mattermost-desktop"
display name (package.json: productName) is "Mattermost"

gulpfile.js

@@ -148,7 +148,6 @@ function makePackage(platform, arch, callback) {
   var packageJson = require('./src/package.json');
   packager({
     dir: './dist',
-    name: packageJson.name,
     platform: platform,
     arch: arch,
     version: require('./package.json').devDependencies['electron-prebuilt'],
@@ -160,10 +159,10 @@ function makePackage(platform, arch, callback) {
     "version-string": {
       CompanyName: packageJson.author,
       LegalCopyright: 'Copyright (c) 2015 ' + packageJson.author,
-      FileDescription: packageJson.name,
-      OriginalFilename: packageJson.name + '.exe',
+      FileDescription: packageJson.description,
+      OriginalFilename: packageJson.productName + '.exe',
       ProductVersion: packageJson.version,
-      ProductName: packageJson.name,
+      ProductName: packageJson.productName,
       InternalName: packageJson.name
     }
   }, function(err, appPath) {
@@ -200,6 +199,7 @@ gulp.task('sync-meta', function() {
   var appPackageJson = require('./src/package.json');
   var packageJson = require('./package.json');
   appPackageJson.name = packageJson.name;
+  appPackageJson.productName = packageJson.productName;
   appPackageJson.version = packageJson.version;
   appPackageJson.description = packageJson.description;
   appPackageJson.author = packageJson.author;