Fixes bug with add flag on a page with multiple classes.
Adds class flag creation/modification time filters.
Adds flag creation and mod time uneditably to admin panel.
Fix link in flag query results when no results are found.
Adds scheduling status to flag query builder.
Improves query performance of class flag query results.
Changes flag-extra to a class rather than an id.
Fixes some more duplicate ids.
Fix class flag numbers on dashboard.

Previously they showed flags for any program.  This was not the intended
behavior.
Merge branch 'main' into class-flags

Conflicts:
	esp/esp/program/admin.py
Remove some one-letter variables in class flags
Update docstrings, wrap lines.
Change some english text in class flags.
Move classflags js around
Corrects typos in documentation
Use STATUS_CHOICES instead of hardcoded statuses
Merge branch 'main' into class-flags
Merge pull request #1234 from learning-unlimited/class-flags

Merge branch 'class-flags' into main

Various fixes and improvements to class flags