Client|Console: Dragging log's top edge with the mouse

Todo for later: Could use some further usability tuning. E.g., if the
user resizes the log with the mouse, does it mean expansion should be
disabled? (maybe user wants the log to have a specific height)
Refactor|Server: Added ServerApp

The old procedural app initialization is now handled by the ServerApp
class, modeled the same way as ClientApp. Naturally the base class
is de::TextApp instead of de::GuiApp, though.