[flatpak] new update model for flatpak 1.0.X

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Flatpak:
     - allow the user to choose the installation level: **user** or **system**
     - able to deal with user and system applications / runtimes
+    - able to handle partial updates for Flatpak >= 1.5
     - new configuration file located at **~/.config/bauh/flatpak.yml** ( it allows to define a default installation level )
     
 ### Improvements