Provide a stable and beta version

[Lion1971]

It would be good if there would be two version online. A stable and a beta version.

For paraglider who would like to use the variometer mainly for flying for a long time, it would be helpful, if there is a always a stable version for e.g. 6 - 12 month with a defined feature set.

For more technical users who are looking for the newest features and like to test and upload the code more often, a beta version can be provided which becomes a new stable version after beta testing and feedback from the beta users.