websocket implementation

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>
added event topic

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>
Added event entity, dao and service

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>