I now excluded all languages that got less than 50%.

We got this mail from Transifex:

> A resource could not be auto-updated
>
> Transifex was unable to auto update the file Briar Desktop. Fetching
from the following URL failed
https://code.briarproject.org/briar/briar-desktop/-/raw/main/src/main/resources/strings/BriarDesktop.properties.
The error message from the server was:
>
> Invalid plural types for string: expiration.banner.part1. Language
supports: ['one', 'other'], but found: ['zero', 'one', 'other'] instead.
>
> Please make sure the URL provided for the file is accessible, or
update the link to the file.
> If you plan to stop auto-update for this file, please disregard this

Fixes #241

The conversation already gets closed when deleting a contact.

Briar Android's shutdown is handled in `BriarService::onDestroy`

https://code.briarproject.org/briar/briar/-/blob/a53a49e543e3190f329b8608ecec157da4047b89/briar-android/src/main/java/org/briarproject/briar/android/BriarService.java#L206

and `BriaService::shutdownFromBackground`

https://code.briarproject.org/briar/briar/-/blob/a53a49e543e3190f329b8608ecec157da4047b89/briar-android/src/main/java/org/briarproject/briar/android/BriarService.java#L264

There, there are some more Android specific stuff like wakelocks,
`stopForeground()` and `unregisterReceiver()` calls, but in general it
does the same like Desktop: call `stopServices()` and then
`waitForShutdown()`.

As part of this TODO search, I created the following issues and
comments between those two chat logs:
* https://chat.briarproject.org/briar/pl/xq3oewf8q7b7mmzryp7dsimawy
* https://chat.briarproject.org/briar/pl/axa877burpypufhmkb8r4k8m6a

Besides this single TODO I found no other TODO comment either important
enough to create a new issue or comment or eligible to get removed.

Fixes #140

Add jackson_version as this is now required by bramble-core's
build.gradle.

Extend feature flags implementations in our modules and disable private
groups, forums and blogs in core.