Pref: default torrent file handler

Before, the app made itself the default torrent file handler automatically, pissing off some of our users. Now, it's not by default, and you can change it in the prefs.

src/main/ipc.js

@@ -8,6 +8,7 @@ var app = electron.app
 
 var dialog = require('./dialog')
 var dock = require('./dock')
+var handlers = require('./handlers')
 var log = require('./log')
 var menu = require('./menu')
 var powerSaveBlocker = require('./power-save-blocker')
@@ -91,6 +92,14 @@ function init () {
   ipc.on('showItemInFolder', (e, ...args) => shell.showItemInFolder(...args))
   ipc.on('moveItemToTrash', (e, ...args) => shell.moveItemToTrash(...args))
 
+  /**
+   * File handlers
+   */
+  ipc.on('setDefaultFileHandler', (e, flag) => {
+    if (flag) handlers.install()
+    else handlers.uninstall()
+  })
+
   /**
    * Windows: Main
    */