REL: Release 0.15.0

CHANGELOG.md

CITATION.cff

build.properties.d/00_default.properties

src/core/js/edit_mode.js

src/core/js/fileupload.js

src/core/js/form_elements.js

src/core/pics/logo_linkahead_no_subtitle_231x40.png

src/doc/conf.py

src/doc/tutorials/edit-lazy-load-dropdown.png

src/doc/tutorials/edit_mode.rst