debug mode: make fs writable

otherwise, people have to use CLI tool.

src/js/client.js

@@ -739,7 +739,7 @@ angular.module('Application').service('Client', ['$http', '$interval', '$timeout
     Client.prototype.debugApp = function (id, state, callback) {
         var data = {
             debugMode: state ? {
-                readonlyRootfs: true,
+                readonlyRootfs: false,
                 cmd: [ '/bin/bash', '-c', 'echo "Repair mode. Use the webterminal or cloudron exec to repair. Sleeping" && sleep infinity' ]
             } : null
         };