Merge branch 'f-edit-mode-drop-zone' into 'dev'

CHANGELOG.md

src/core/css/webcaosdb.css

src/core/js/edit_mode.js

src/core/xsl/entity.xsl

src/core/xsl/main.xsl

src/core/xsl/messages.xsl

test/core/js/modules/edit_mode.js.js