Make Portable App also a Silent App

Fixes two portable app bugs, to make the app fully "silent", not just
"portable". This means that not only are all data files stored in the
"Portable Settings" folder, but the app should leave no trace on the
host system.

- Disable Electron's single instance mode so no lock file is created in
"%APPDATA%\Roaming\WebTorrent".

- Put Electron crash files, and other electron files into the "Portable
Settings\Temp" folder instead of "%APPDATA%\Temp".

src/main/index.js

@@ -33,9 +33,11 @@ if (process.platform === 'win32') {
   argv = argv.filter((arg) => !arg.includes('--squirrel'))
 }
 
-if (!shouldQuit) {
+if (!shouldQuit && !config.IS_PORTABLE) {
   // Prevent multiple instances of app from running at same time. New instances
-  // signal this instance and quit.
+  // signal this instance and quit. Note: This feature creates a lock file in
+  // %APPDATA%\Roaming\WebTorrent so we do not do it for the Portable App since
+  // we want to be "silent" as well as "portable".
   shouldQuit = app.makeSingleInstance(onAppOpen)
   if (shouldQuit) {
     app.quit()
@@ -48,7 +50,11 @@ if (!shouldQuit) {
 
 function init () {
   if (config.IS_PORTABLE) {
+    const path = require('path')
+    // Put all user data into the "Portable Settings" folder
     app.setPath('userData', config.CONFIG_PATH)
+    // Put Electron crash files, etc. into the "Portable Settings\Temp" folder
+    app.setPath('temp', path.join(config.CONFIG_PATH, 'Temp'))
   }
 
   const ipcMain = electron.ipcMain