casting tests

I checked in a few casting tests at:

http://www.w3.org/2001/sw/DataAccess/tests/data-r2/cast/manifest.ttl

There's one test per cast function. They don't (attempt to) test every 
combination of input type + cast function, but they should test that an 
implementation has implemented something sensible for the cast functions.

Please report on how you do against these tests. Glitter doesn't do cast 
functions yet, but I tested these against the ARQ deployed at sparql.org 
and manually eyeballed the results.

I also fixed the XPath for the cast facets (which was too liberal 
before) and am currently regenerating the coverage information. (I 
expect to still have some missing facets remaining.)


Lee