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.

The main effect is that fitsharp's own story tests now assume they run from the directory of the Runner binary, e.g. build/debug or build/release, not from the fitsharp root directory.

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?