Unification of Google Play Store (Yalp/Aurora) and F-Droid

In App Manager, our goal, as always, is to unify features and remove the burden of using another application.

Currently, we've included Aurora Store, APK Updater and F-Droid in various pages so that the user can easily open the apps as if they are part of the app. However, this model doesn't work very well since App Manager, like any other package managers, should be the source to download, install and update applications. In order to achieve that and reduce burden on the main app, I propose another extension that merges both Google Play Store and F-Droid.

**Features**
- Download or install APK files (along with update checking ability on app info page)
- Display descriptions, changelogs and exodus report (and when the download is complete, display our favourite **what's new**)
- Automatic handling of architecture and version codes
- Similar apps section (when enabled)

**Privacy features**
- Orbot integration
- Google Play Store disabled by default

**Obstacles**
- For Google Play Store, we need a token dispenser server which doesn't go with our model. So, whether we can actually support Google Play Store is still hanging in the air. However, if we implement such feature, a custom field will be added where the users can insert custom dispenser server such as Aurora's.
- APK Mirror, APK Pure are alternatives but they may not be used because the former doesn't allow direct download of APK files and the latter is unreliable.