Merge remote-tracking branch 'origin/master' into copy-paste-math-v2

Conflicts:
	src/plugins/oer/assorted/css/image.css
Merge pull request #90 from oerpub/57878870-arrow-instead-of-circle

for tables, preview insertion spot with arrow instead of circle
Merge pull request #95 from oerpub/improve-header-styling-58912428

make the "copy section" same/styling as other "copy [element]"s
Merge pull request #84 from oerpub/copy-paste-math-v2

Special copy/paste handler for math.
remove ephemeral classes that were present on copy
Merge remote-tracking branch 'origin/make-pasted-block-look-unselected-59024166' into testing