Fix: skill gui live search

Change skill gui to make skill searches work without updating from memory.

• For that, we add a Snapshot (skill state) to the memory abstraction wrapper of the gui. All widgets can always get the latest known state from the wrapper, without having to make an ice call. This is necessary, as widgets do not, and should not hold state.
• Currently the timer widget sends an "update yourself, now!"-signal to all widgets that wish to interact with the memory. This needs to change, as there would be a race between the wrapper updating itself, and the widgets accessing the update.
• Solution: the wrapper gets the "update" signal from the timer widget, and once done, emits a signal to provide the update to all affected widgets. This is similar to the principle used in https://git.h2t.iar.kit.edu/sw/mice.

Todos:

• Add snapshot struct
• Update wrapper to use snapshot
• Update widgets to passively receive updates