leave report: add filter for dept employee appt status

[jxjj]

This adds a new filter to the Dept Leaves report, allowing users to choose whether to show only currently active dept employees or all department employees.

UserService::getDeptInstructors() is updated to add a new hasActiveDeptAppointment property to each instructor. The method adds an api request to Bandaid to get the current dept employee list, and then compares this active list with the list of all instructors. We could probably optimize this further (maybe just returning the active status directly from bandaid?) if needed.

On the frontend, the a new onlyActiveAppointments filter is added to the course planning store. By default, this is true – only active instructors will be shown in the report.

One gotcha was with the TA tab – the new 'only active' default seems to prevent any TA's from being shown (presumably because these TA's are not considered dept appointments). As a workaround, if a user clicks the TA tab, the filter will automatically change to "All". It's a little hacky, but simple and might be good enough – we could look at other solutions, tho.

Let me know if any labels or UI elements should change.

On dev.

Known issue: tests need to be updated.

Resolves #204

[cmcfadden]

looks good - is the test failure something to be concerned about?

[jxjj]

update: test fixed. Needed to stub bandaid response to /department/*/employees for one test since we're now calling that endpoint to determine if instructor is current. (Other tests were already including this, but this test clears those to substitute it's own response).