implemented generation of anon names

[VcSaJen]

Before you begin

• I understand my contributions may be rejected for any reason
• I understand my contributions are for the benefit of Ponybooru and/or the Philomena software
• I understand my contributions are licensed under the GNU AGPLv3

• I understand all of the above

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So, there it is. Generator for anon/bp names like "Western Drums #F447" or "Worrisome Door #FB44". It's in the server code, not in JS, so it would work for users with disabled JS. Do you think it's worth it to add? Or not? I'm fine with either way.
One thing to note: if users reply "@Brilliant Marmalade #1582" in their comments, it will remain so regardless of anything, because it's a static text.
Performance is not much different than SVG Background Pony avatar generation, because it was based on that code.