Implement playable challenges into frontend

[mtemnov]

Implement playable challenges into frontend

[mtemnov]

Requirements:

• the /challenge site has to contain the "play" functionality (backward switch probably not required?)
• switches which have to hold a marble in the end state should be highlighted in a color (e.g., red)
• once the respective switches hold a marble, the color should switch (e.g., to green)
• once all required switches are green, there should be a "winning popup"
• there should be a hint (e.g., question mark with hover) which explains the challenge goal

[mtemnov]

Done in last sprint