Allow Release builds with the build command.

- build.proj sets the current working dir to build/$(Config)
- storytest.config.xml paths rebased per the above
- All affected test pages rebased per the above
- Net result: uglier test pages, but you can do:
  $ build "/p:Config=Release"
  and have build, unittest and storytest happen
  on the built release binaries.

I'm sure there are more principled ways of doing this, but I just want to get a consistent build procedure in place. Does this update make sense?

Its main effect is that you must execute fitsharp's own tests from the directory of the Runner binary, e.g. build/debug or build/release.