Fixes issue #3611925.

Fixes issue #3611959.

Only the ARM binary is included at present. Better control of the Tor
process is needed - it's possible for it to be left running when Briar
exits, and if the cookie file is deleted it's no longer possible to stop
the process.

If the group's owner is spamming, unsubscribe.

This keeps the visual language consistent: rating icon plus name equals
author.

This depends on the (unspecified) order in which new secrets are stored.
For example, if the secrets for periods 0 - 2 are loaded in period 3,
the secrets for periods 3 and 4 will be stored; the secrets for periods
0 and 1 may expire separately if the secret for period 3 is stored
before the secret for period 4, or together if the secret for period 4
is stored before the secret for period 3.