Create viewer for writing responses in NCME study

[bxie]

For a given user in the NCME study, select a problem and show the following:

• final code output
• intermediate code outputs at uniform intervals (e.g. every 60 sec), where these intervals can be user-defined

TODO:

• [x] create /viewer endpoint and limit to those where "UsersNcme2019/{uuid}/isAdmin" is true
• [ ] get dropdown of all ncme users (emails and exerciseAssignmentId)
  • [ ] can't get email unless use firebase function, so just uuid and condition. see stack overflow answer
• [ ] when given user selected, show dropdown of all ncme exercises (ExerciseId) where ExerciseType is "WRITE"
• [ ] for selected write exercise, show exercise view w/ value written in at certain hime
• [ ] have restricted slider to go between intervals
  • [ ] marks are normalized datalog timestamp (minus start time, converted to sec)
• [ ] have a forward and back buttons to move slider a user-defined positive value of seconds (e.g. 30 sec)

Data structure for a user