It's always a good idea to not use reviews.

Spoiler message support has been added to QXmpp recently (by me).

Co-authored-by: Linus Jahn <lnj@kaidan.im>

This replaces the old libnotify-binary based notifications (executing
shell commands) by cross-platform working notifications provided by
KNotifications.

Currently the dependencies (knotifications and its dependencies) are not
built on the CI for the most platforms (android, macOS, windows, ut),
however knotifications would also work on these platforms.

Currently translated at 100.0% (98 of 98 strings)

Currently translated at 100.0% (98 of 98 strings)

Translate using Weblate (Czech)

Currently translated at 99.0% (97 of 98 strings)

Currently translated at 93.3% (97 of 104 strings)

Currently translated at 100.0% (120 of 120 strings)

Currently translated at 89.5% (85 of 95 strings)

Currently translated at 100.0% (82 of 82 strings)

Added translation using Weblate (Galician)

Currently translated at 76.8% (63 of 82 strings)

Added translation using Weblate (Arabic)

This rewrites parts of the main database class. All classes working on
the database have been moved to the new database thread, so inserting
records into the database isn't blocking the user interface anymore.
What also improved the performance *massively* is the use of SQLite
transactions, when inserting multiple records. So inserting is so fast
now that it actually wouldn't necessarily require another thread, but
with this we're safe in the future.

The message model and the roster model have been splitted up into a
database manager and the list model that is used to present cached data
to the user. The XMPP managers are connected to both the model and the
db classes, so both are updated in parallel.

There are also two new classes for the RosterItem and the Message,
because we need to cache those in the models in a vector. The Message
class inherits from QXmppMessage, so we can now use the same class for
sending messages and inserting messages into the database.

Closes #273.

This bring better performances for low power devices and allow better
 and easier filtering from a proxy.

This fix the emoji picker to present the real system emoji that would
 appear in the message view.
There is no reason to present emojis for a font the message view will
 not render identically.

Currently the failing windows build blocks all artifacts on the website.

QtCreator can now recognize the QML files.
This also avoids binary incompatibility issues.

There were several problems with the settings layer (on mobile):
 - You could open the settings layer multiple times
 - When you logged out while being in the settings the settings layer
   didn't disappear

Fixes #279.

This is only useful on Android and on other platforms supporting this on
the virtual keyboard.