Optimize and unify markup of SVGs and align to
WikimediaUI color palette where easily applicable.
Also removing three unused image files.
Bug: T153043
Bug: T178867
Change-Id: Ied457ef84357374e66db9e1936ce1b754d53cfdb
Based on the discussion on T56307, this change is controversial
and not necessarily wanted. In summary:
* Green star looks out of place with blue Vector (Edokter, Esanders, Trevor)
* Clashes with WikiLove heart icon (Edokter)
* Flat design doesn't fit with Vector's gradient style (Rillke)
* Green means constructive in MediaWiki UI, however clicking the
green star removes a page from your watchlist (Krinkle)
This reverts commit 56825d209e.
Change-Id: I46f75a0eb83f9643fc0b51befe02aad4a84efc4e