Proposal: deprecate silk icons theme

[MichaelHamann]

@vmassol

Isn’t the image:icon: syntax using the current icon theme? Does it mean it’s a syntax only supporting the Silk icon set? If so, that’s bad and we need to do something about this syntax (fixing it in xwiki/2.2, etc).

The problem has two sides:

1. This is an image syntax that is defined by xwiki-rendering. We just resolve the reference to an actual image in xwiki-platform. As this is an image syntax, this would require quite some hacks to support icon fonts. Afaik SVG is only a workaround if the icon theme supports SVG, we can’t simply produce SVG images for an icon font.
2. CKEditor expects that when you use an image syntax you get an image that has, e.g., a width and height that can be modified or an alternative text. All of this doesn’t work with an icon font.

As a solution for this, I introduced the icon macro some time ago. It allows displaying an icon from the current or a chosen icon set. My suggestion back then was to deprecate this icon reference syntax, i.e., to still support it but to not offer the option in the UI when adding or editing an image that is not already an icon.