SimpleX installation with Flatpak

• install, update, remove, version functions
• persistence of application and user data
• Flatpak integration
• over Tor: HTTP_SOCKS/HTTPS_SOCKS variables are not read by SimpleX, but toggling Settings>Network>Enable Proxy button is enough
• tested on Tails. Linking with a phone is only possible from the same local network, but I made tests from a VM and I have not tested it
• tested on Debian