[webdoc110] Webdoc: describe Beam API; rm unused shortcodes ()

Device/Beam/Beam.h

devtools/code/hugo-shortcode-usage.py

hugo/content/py/instr/beam/_index.md

hugo/content/py/sample/multilayer.md

hugo/layouts/shortcodes/collapse.html

hugo/layouts/shortcodes/readfile.html

hugo/layouts/shortcodes/ref-api.html

hugo/layouts/shortcodes/ref-manual.html

hugo/layouts/shortcodes/ref-tarball.html

hugo/layouts/shortcodes/toc.html