ProjectExpressions examples

All,

I've tried to faithfully distill examples of ProjectExpressions from the discussion we had (thanks for contributing!), and put it in the wiki:
http://www.w3.org/2009/sparql/wiki/Feature:ProjectExpressions#Example

I decided to keep fn:concat(), since it was a pretty useful example of something one may want to do and indeed, the arguments against it weren't very strong. I put a reference to Xpath F&O in our F&R, and I use that reference in the wiki.

Then, I put in only one example of a CONSTRUCT, the one with a subquery. While I felt this is a bit too complex for the examples of this document, it seems to me that it is also quite clear how it should be done. As opposed to a CONSTRUCT where the function is in the ConstructTemplate, which is very useful and interesting, but it seems to require more discussion, especially to make it stand apart from the list shorthand syntax. I put a reference to the subquery section along with it.

I think what is now in the wiki is acceptable, but I have not yet committed it to the document. I'd like to encourage those who are interested to make edits to it, and I'll commit what is there just before the teleconf. 

Cheers,

Kjetil