Flatpak migration

Flatpak:

• Rewrite chat message deprecated logs : no more ensuring that this file must exists
• If a message history file exists in the application folder, let the SDK migrate data and remove the file
• Copy recursively all data from Flatpak installation, if files doesn't exist
• Split 2 migrations : old GTK and Flatpak

Need of MR linphone-sdk!1056 (merged) in order to avoid having no logs in timeline