gui: remove unused method from Preview class

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
gui: better message style preview code

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: remove unused code in chat styles

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: fix crash

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: do not derive style engines from QObject

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: improve memory management in ChatStylesManager

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: fix preview messages

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: remove unused method from ChatStylesManager

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat: some file renaming and class moving

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
gui: create separate widget ChatStylePreview

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
misc: introduced qobject_ptr

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
gui: simplify Preview widget

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>