added shuffle stack shortcut

[RomanNovo]

Fixes/Solves Solved Issue-111

111

For default key is Z

[RomanNovo]

1. Added
2. In original Tabletop (actually checked right now) Shuffling with multiple pieces selected shuffled them separatly.
3. Again, in original version, select stack is not required for shuffled. Hover is enough

[drwhut]

With the echo events, the client sends requests to the server around every 30ms, which is too fast in my opinion.

We can either:

• Keep detecting echo events, but add a timeout to request_shuffle on the server side (e.g. 500ms, or 1000ms?)
• Not detect echo events.

[RomanNovo]

Screw this. Save idea for later. Will delete echo event