site(customize.html): #1144 - Allow multiple endpoint selections

This fixes the customize.html form  to allow users to select more
than one endpoint handler.

I guess this fixes #1144
Merge branch 'site/multiple-endpoints' into site/4.4

* site/multiple-endpoints:
  site(customize.html): #1144 - Allow multiple endpoint selections
fix: #1144 - Error when selecting traditional
site: #384 - Allow total progress custom builds
site: #1061 - Allow image scaling in custom builds
refactor: Move image-related modules to be near each other