Improve network efficiency out of db

[patudom]

all_data galaxy measurements include things that we actually need to pass back and forth. For example, for the Hubble viewer class slider, we only need to keep:

• student_id
• galaxy_id
• velocity_value
• distance_value
• class_id

For summaries:

• class_id or student_id
• age_value

As we go, we can think of other places where we can improve efficiency.