gui: add WebkitMessagesViewDisplayFactory

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
gui: add two implementation of WebkitMessagesViewDisplay

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
chat-style: import prune settings from previous versions

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
gui: select WebkitMessagesViewDisplay basing on cfgNoHeaderRepeat()
gui: fix adding new messages in no-header repear mode

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

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