Add placeholder UI for showing replies in the text entry widget.
Existing quoting capability has been removed (Temporarily), as
it was replaced with the new reply capability.  Replies sent from
nheko do not currently appear correctly in the timeline (this
will be fixed in a future commit).

- Update version numbers and documentation
- Fix github releases oauth key

This reverts commit 4b807229.

Add initial loading of qt jdenticon plugin:
https://github.com/redsky17/qt-jdenticon

Currently, the library's functionality has not been integrated
into the rest of nheko.  Next step is to add a configuration
item in the User Settings and use the plugin to generate
avatars for users without their own picture.  These avatars
should be cached in the Cache object.

fixes #79

fixes #437

fixes #283

When the object is destroyed the connections will be removed
automatically by Qt.

fixes #433

* Working D-Bus desktop notifications

* Remove return type on constructor

* Fix the Windows placeholder class

* Fix wrong variable name

* Fix windows and macOS versions of notificationsmanager