Selecting on the alt attribute is unstable and creates a non-obvious
coupling to maintain. Also it inadvertently affected the shop banners
and some elements in settings.
The need for sidebars to have access to macros.random_image means
all templates that include header.html (most templates) need to have
access to `macros`, because header.html includes sidebar_{SITE_NAME}.
Because of how sparse helpers was, we instead unify the two and
replace it since I know we had helpers in every top-level template.
Aevann1
gooseman
Snakes