Update background

[rtibbles]

Summary

• Cherry picks Refactor default_theme paths/structure #12207 back into 0.16.x where it was meant to be targeted
• Updates the background image for the rebrand
• Updates how we display the background image, allowing us to apply a blur filter on compatible browsers (most browsers that we support, except IE11) to prevent the image looking lower quality on higher resolution screens. This was previously masked by the use of a higher opacity overlay on the image, but this has been reduced in order to make colors in the background image more vibrant.

[nucleogenesis]

I ran it locally and it looks awesome -- totally jives with the new theme much better.

Just one question - why the move of the static/assets/default_theme into kolibri core from the default_theme plugin?

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.2b2.dev0_git.15.gadfd1442.pex
Windows Installer (EXE)	kolibri-0.16.2b2.dev0+git.15.gadfd1442-windows-setup-unsigned.exe
Debian Package	kolibri_0.16.2b2.dev0+git.15.gadfd1442-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.2b2.dev0+git.15.gadfd1442-0.4.2.dmg
Android Package (APK)	kolibri-0.16.2b2.dev0+git.15.gadfd1442-0.1.3-debug.apk
TAR file	kolibri-0.16.2b2.dev0+git.15.gadfd1442.tar.gz
WHL file	kolibri-0.16.2b2.dev0+git.15.gadfd1442-py2.py3-none-any.whl

[rtibbles]

Just one question - why the move of the static/assets/default_theme into kolibri core from the default_theme plugin?

This was a result of my putting a lot of these images in the wrong place, and then @marcellamaki cleaning them up somewhat. But I do think they could be put into the default theme plugin static folder instead of the core static folder (that was a result of my miscommunicating the cleanup to @marcellamaki, and missing this when I merged the PR). Will clean up now.

[rtibbles]

Updated!

[nucleogenesis]

Thanks for clarifying! Code / dir updates look good

[radinamatic]

Looking good in 3 browsers on both Ubuntu 20.04 and Windows 10:

Ubuntu	Windows

[radinamatic]

LGTM,