Merge apps and system modules to Plinth Core
Created by: sahithi-ihtihas
I made the changes mentioned in this comment and created a pull request
Move templates from the "apps" and "system" modules into plinth/templates.
Move routes from apps and system modules into plinth/urls.py.
Move views from apps and system modules into plinth/views.py.
Rename things as needed so they don't conflict with existing items.
Basic testing to check that nothing is broken.