Permissions view creates empty files in home folder

[meisenzahl]

Closes https://github.com/elementary/switchboard-plug-applications/issues/121

[meisenzahl]

Fixes a recursive constructor invocation

• AppManager.construct ()
• AppManager.get_apps_for_installation ()
• App.construct ()
• App.get_overrides_path ()
• AppManager.get_default ().user_installation_path

At that time AppManager was not yet completely created...