Use @xml:id from <wadl:resources> in DocBook as part of generated section xml:id

This will make it possible to avoid duplicate ids even pulling
in content from wadls with the same paths, method names, etc.
This also avoids the need to add xml:id attributes on
wadl:resources elements in the wadls themselves.

Change-Id: I397c6cb9a313d3d1729029b351fa89953a71d158
Merge "Use @xml:id from <wadl:resources> in DocBook as part of generated section xml:id"