Implement changes to screen 4 from the 1/14/2025 design meeting

[jbphet]

We had a design meeting yesterday, Jan 14 2025, where most of the time was spent reviewing and refining screen 4. There's a fairly big list of items to implement as a result of this meeting. I'll put a summary list below, and more detail on these can be found in the "Meeting Notes->January 14, 2025" section of the design document.

• Change the term "Basis" in the Measurement Parameters box to "Measurement Axis
• Change layout of multiple spheres and atoms to 3-2-3-2
• Remove the equation in the experiment area (i.e. the right side) in the "Multiple" case
• Clear the histogram data when any changes are made to the preparation Bloch Sphere or anything else that changes the nature of the measurement
• Change the behavior such that no precession occurs until the measurement starts
• Make the magnetic field representation ephemeral until the measurement starts, then more solid looking, then ephemeral when done
  • Make sure all colors are in the color profile
• Update the equation above the Bloch sphere in the measurement area to match the measured state when the measurement occurs
• Add the ability to select the measurement basis in the equation above the Block sphere in the experiment side
  • The arrows should have subscripts depicting the basis
  • The term should be "Basis"
• Remove labels on the small Boch spheres and make the vector thicker
• Change the radio button labels for "Single" & "Multiple" to the icons that should be in the notes in the design doc
• Make the button say "Start" instead of "Observe" in the timed observation case
• Have the button be green for Start or Observe and cyan for "Reprepare"
  • Make sure colors are in the color profile
• Add an Erase button to clear the collected data (mostly shown in the histogram)