change mKR relation to SPARQL compatible CSV format

[rhmccullough]

I gave up on my old repository and created a new fork. I examined the diff very carefully to make sure I did not undo any of your recent unsigned changes. The new function I added to the bottom of raptor_turtle_writer.c is adapted from Rasqal code. All makes succeed.

[rhmccullough]

I introduced the Linux "load twice" bug when I was trying to load the new CSV function with mkr, but not with turtle. I did not detect the bug because "load twice" is not an error on Windows/Cygwin.

[rhmccullough]

return void error caught by clang and c++ compilers

[rhmccullough]

string cast error caught by c++ compiler

[dajobe]

Looks good, merging