Feature/add people tool

This includes changes for displaying member count for each section, on the page that displays the list of sections. The UI has also been modified to reflect the count.(As of now all the enrollees will be displayed. If there are people having 2 roles within a section, they will be counted separately. If it's determined that this needs to change, additional filters could be applied, but the  base method would still remain the same)
This is a more general question than just for this piece of code, but do we have any non-functional requirements around performance? It feels like if we have a large number of sections each with a large number of students this could get expensive.

One observation is that we don't actually need to get the full list of section enrollments (just the count). For, say, 100 enrollments with a maximum page size of 10, fetching all enrollments just to count the elements and throw the list away will require ten API calls (linear time). If we just want the count, we could:
 - Fetch the first page of ten results.
 - Look for the 'last' link in the header.
    - If that link doesn't exist, return the number of elements on the first page.
    - If the link does exist:
       - Inspect the 'last' URL to get the page parameter
       - Fetch the last page
       - return ((page - 1) * per_page) + (count of elements on the last page) 
This way the method runs in constant time, with a maximum of two calls regardless of the number of elements.