Feature/section tool cs

Refactored add people tool to open directly in 'Manage Sections' page when navigation link is clicked
Removed the cap_top template, which was the previous landing page for the tool
Views.py:
-renamed cap_top function to ap_top (minor - 'cap' dates from when the project was named 'course add people' rather than 'add_people')
-modified ap_top to redirect directly to create_section_form ('Manage Sections' landing page) rather than    -cap_top for success and appropriate errors
-tool_config modified to default to 'Manage Sections' for menu link text

Urls.py:
changed cap_top to ap_top

create_section_form.html:
transferred error message block which had been in cap_top.html   

tests.py 
Modified one success test; added another
This case, where the course instance id is present in the request but was not found in the database, seems like more of a 404 "Not Found" case than a 500.