Generate entity XML documentation

[Philip Taylor]

We should have some documentation along the lines of XML.Entity for the new simulation system, aimed at people who are writing XML by hand (not writing scripts or C++) or who want an overview of the features supported by entities.

This is probably a precursor to (and obsoleted by) #422 - it's good to have readable offline documentation even if it's duplicated in a cleverer editing tool, and also it's easier than implementing the cleverer editing tool. The documentation should be generated from annotations in the RelaxNG schema so it can be kept up to date and reused. Maybe we also want some extra higher-level documentation for components, derived from the Doxygen or something? The output should probably just be plain HTML files, which can be uploaded somewhere and linked from the wiki.

[philip]

(In [7478]) # Add documentation of the entity template XML file format. Simplify the format a bit. Use less <interleave> in the RNG so that error reports become understandable. Fixes #491.

[(none)]

Milestone OS Pre-Alpha 2 deleted