Remove unmaintained django debug panel in favour of django debug toolbar

[rtibbles]

Summary

• Django debug panel is no longer maintained, and alas, no longer seems to work
• There do seem to be plans to have a proper public API for the debug toolbar data which may allow something similar in the future
• For now, revert to just using debug toolbar
• Simplifies our browsable API interface so that the debug toolbar info is meaningful and about the request made, not extraneous data

Reviewer guidance

Follow the new guidance - does it work?

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.18.0a2.dev0_git.42.g86e1cdee.pex
Windows Installer (EXE)	kolibri-0.18.0a2.dev0+git.42.g86e1cdee-windows-setup-unsigned.exe
Debian Package	kolibri_0.18.0a2.dev0+git.42.g86e1cdee-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.18.0a2.dev0+git.42.g86e1cdee.dmg
Android Package (APK)	kolibri-0.18.0a2.dev0+git.42.g86e1cdee-0.1.4-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.18.0a2.dev0+git.42.g86e1cdee.zip
TAR file	kolibri-0.18.0a2.dev0+git.42.g86e1cdee.tar.gz
WHL file	kolibri-0.18.0a2.dev0+git.42.g86e1cdee-py2.py3-none-any.whl