Resolve Ready Promise after Timeout

iOS 8 sometimes fails to trigger `window.onload` (see #118). Add
timeout to eventually start app regradless of `onload`. Use shorter
timeout on iOS 8.
Merge pull request #119 from tf/ios8-onload

Resolve Ready Promise after Timeout
Reword Multimedia Alert

Replace usages of german "Du" and "Sie".
Background Shadow always Left on Phones
Custom Page Thumbnails for Built in Page Types

Allow overriding the thumbnail displayed in navigation.
fixes typo
Add Audio Loop Page Type

Page with background image and audio loop playing in background. No
player controls.
Merge pull request #120 from tf/audio-loop

Add Audio Loop Page Type
Merge pull request #121 from tf/custom-thumbnails

Custom Page Thumbnails for Built in Page Types
Merge pull request #122 from tf/multimedia-alert-wording

Reword Multimedia Alert
Merge pull request #123 from tf/shadow-phone-pos

Background Shadow always Left on Phones
stub paperclip in encoded file state machine spec
Stricter config access during configure

* Only allow accessing config after configure is done
* Use passed config in after_configure blocks

This ensures files using the config are not auto loaded prematurely
causing usage of unfinished config i.e. in paperclip attachment
options.
Ensure correct Teaspoon::Engine Constant is used.

Teaspoon Spring Command also defines a Teaspoon::Engine.
Add files method to revision and draft entry

Acts as "has_many through" association with variable
source_type. Return files used by revision filtered by given type.
fix wording in german localization
Introduce FileType concept

PageTypes can provide an array of FileTypes which shall be enabled in
the editor when the PageType is registered. FileTypes provide an
abstraction to describe an ActiveRecord model, a json partial and
names for file models like ImageFile, VideoFile, AudioFile.
Turn FilesController from abstract into generic controller.

* Replace concreate image_files/video_files/audio_files routes with
  generic files/:collection_name route to FilesController
* Make FilesController determine FileType by collection name
Use file types in editor seed instead of concreate file classes
Use file types in json template for entries#show