Beta release (Supergroups)

SUPERGROUPS! Test Build!
What is not working and we know it:

• Some supergroup avatars are not showing up
• Small intermittent empty message display during sending
• Member count & list of members in supergroup empty
• You cannot join a supergroup
• Leaving a supergroup needs some time, but it works somehow ;)
• Read indicator shows still always read immediately (wontfix until API-53!)

You are welcome to report all other things you find either here in the tracker or by PM in Telegram ;)

Note: This build modifies the existing database. It should be possible to uninstall/reinstall the stable app without loosing data, but it is not guaranteed. In case of problems it might be necessary to manually remove the whole telegram folder from .config in homedir.