Record retrieval ranges

[michaelyfan]

Implements date selection ranges for getting records. Implemented for both checkin records and route records.

Also fixes a bug that caused record downloads to have incorrect datetimes strings. This was due to Date objects being added to the Excel sheet; the xlsx plugin presumably converts them to datetime strings using the machine's local timezone, which in Cloud Functions's case isn't Eastern. We now add correctly formatted datetime strings instead of letting xlsx handle Date objects.

How to test

1. Install new dependencies with npm i
2. Run the app with npm start
3. Navigate to http://localhost:4200 in a web browser
4. Verify that the "Route Records" page works as intended
   1. verify no bugs in browser console
   2. verify that retrieved records are in the correct range
5. Verify that the "Checkin Records" page works as intended (this page has an extra "View" feature"