[CLEANUP] just the basics

[xerc]

just the basics ; no changes within the ICONs itself
only some where manually edited ; expl. fill twice ..

.. or marked with TODO if it was too obvious that it is not "clean" ; / viewBox="2/
& all occurrences of transform should be re-rendered / cleaned ; / transform=/

fyi/ @ dist/sprites ; strip <?xml version="1.0" encoding="utf-8"?>
style="display: none;" not needet if only <symbols within the file
xmlns="http://www.w3.org/2000/svg" not needet for each <symbol

[xerc]

btw/ @ tmpl/html/docs/_symbol.html.twig ; xlink: is deprecated