New feature: Multi comic handling

In ComicMaster 0063 a new feature has been added: More than one comic can be loaded at the same time. This cannot be used to read two comics at the same time, there are no two displays. However, it is possible to switch quickly between to comic slots and therefore compare the quality of two releases.

Main goal of this release was to open the design to handle more than one comic at a time. Above use case is only the beginning. More features involving multi comics load will be implemented soon.