DAVdroid beta1

Hi, could you please add DAVdroid beta1 as a beta release (see https://f-droid.org/forums/topic/davdroid-alphabeta-versions/)?

For future beta versions, I guess I'll be able to do it myself and send a MR.

The version tag is: https://gitlab.com/bitfireAT/davdroid/tags/v1.0-beta1 (commit: 8449684d)