Integration with external applications

We should select the best open-source applications we can use with ARK Navigator:
_e.g._ image editor can be called by [edit] button from gallery mode.

We should fork those applications and add support of our application:
_e.g._ image editor should know where to locate _root folder_ of resource's new version to save.
_also_ it might call ARK Navigator back in order to label new version with tags of old version.

We should have options to install our versions of these apps in Settings screen (#77).
Any call to external application should check if one of our versions of these apps is installed and can handle the call:
* If yes, we should open it directly without asking the user.
* If no, we should open app chooser and remember the choice (current behaviour).
Such a choice should be possible to reset in Settings screen.

No files or tests are named. Start by reviewing the gallery-mode edit action and Settings issue #77, then identify the external-application call flow and the applications to support; done would require integrated app versions, installation settings, automatic handling when available, and configurable chooser behavior.

Written by the indexing model from the issue text.