docs: Merge xsd-fu prerequisites into build instructions

Merge source code page with build instructions
Move build instructions to the top since it's got a wider
scope than contributing--non-developers need this
docs: Correct incomplete sentence
docs: Correct genshi notes
docs: Simplify crossreference
docs: Rework git links
docs: Further rework git links
docs: Update generateDS URLs
docs: Document use of core.autocrlf=input on Windows
Merge pull request #1208 from rleigh-dundee/xsdfu-genshi-docs-develop

docs: Merge xsd-fu prerequisites into build instructions (develop)