Order nodes in sitemap by priority descending

Problem/Motivation

It seems like the order of items in a sitemap is content type name, which can result in the most important nodes getting placed at the very end.

This is unfortunate, since if you have a lot of unimportant nodes placed first in the sitemap, a crawler could skip the last nodes, or in best cases, crawl them last, when you'd like them to get crawled first.

Steps to reproduce

A web site has two content types:

• "Alphabetizer" with 1'000'000 nodes are the least important
• "Zero hero" with 10 nodes are the most important

1. Create a site map with the two content types, set priority for "Zero hero" to 1.0 and "Alphabetizer" to 0.1
2. Generate a site map
3. See that the 10 "Zero hero" nodes are placed in the last site map, at the end

Proposed resolution

Order nodes in site maps by priority descending, to ensure the most important nodes get crawled first.

Remaining tasks

User interface changes

API changes

Data model changes