Coach can report session durations as-needed to capture variable session durations

This is an additional enhancement to https://github.com/AmericaSCORESBayArea/AmericaScores-CoachApp/issues/18

The reality is that sessions often go as much as 2-3x longer than is assumed in the current 1 session=1hour reporting. This is especially true of "game day" sessions that happen fridays and weekends.

The underlying salesforce schema is already needing update to accommodate the 1.25 hour sessions that are being reported to the Oakland (OFCY) system.

A coach-facing feature is needed to bring all apps and data in-line.

Example MVP:
1. Coach selects "Start a Session Now" from the home screen
2. A Timer Starts immediately, running in increments of 15 min.
3. At any time while in-session the coach can select the session that is being timed
4. At any time while in-session the coach can take attendance
5. At any time a button is accessible that will pause/restart or end the timer
6. When the timer ends, the coach is required to assign the duration to a specific session by selecting from their session list for that day or using the edit/add session flow described in https://github.com/AmericaSCORESBayArea/AmericaScores-CoachApp/issues/18
7. The coach can Cancel the action of saving duration but only after confirming their intention "Are you sure you want to cancel and not report hh:mm to a session? (Y/N)"

*Dependencies*
DB Change
https://github.com/AmericaSCORESBayArea/salesforce-environment/issues/4
DATA-API Change