Align SVG markup across Foundation products by:
- unifying XML declaration,
- removing unnecessary `standalone="no"` attribute as it's default,
- removing unnecessary `enable-background` attribute as it got removed
from standard
- removing all SVG editor metadata
- adding `width` and `height` attributes where missing,
- removing all `g` group elements except where necessary for transforms,
- putting attributes on `path`,
- removing unnecessary ids and
- unifying whitespace.
Also
- changing 'expand' and 'gear' icon colors to resemble general button style,
- while at this renaming 'gear_gray' to 'gear' including CSS reference,
- slightly adapt remaining colors to WikimediaUI color palette and
- deleting unused, unreferenced icon files.
Saving up to 79% file size before gzipping.
Bug: T178867
Change-Id: I9e54a3a972903811f5205def05397383f3484d63
