This change adds the ability to run Nheko without a secrets storage
service[1]. The secrets are stored in plaintext under the [secrets]
section of nheko.conf. Since this is a "I know what I'm doing" type
of feature, it's disabled by default and can only be enabled with an
hidden setting `run_without_secure_secrets_service=true`.

Fixes issue #705.

[1]: https://freedesktop.org/wiki/Specifications/secret-storage-spec

Fixes messages in room flickering and being stuck

fixes #760
relates to #770
relates to #789

Showing the bootstrap state and showing there are unverified devices is
still missing.

Added support for refreshing the device list, marking current device with a checkmark instead of a lock

There is not really a reason to stop tracking them, just because the
server says so. We might still want to show a users profile, etc.

This fixes spaces or stickers not showing up for old databases as well
as the wrong format of the state_keys db.

Also fixes some issues where nested transactions will poison the
verification cache.