Rename FileSystemContext to FileSystemBinding.

It's confusing having objects that go into the context named *Context.
Always build in parallel.
Remove wrapper task.
Some cleanup on the manual's build script.
Change sass configuration to not build into a versioned dir.
Don't always build in parallel, as the maven wagon stuff is not threadsafe.
Some build configuration simplification.
Javadoc the file package, and some simplifications on file system binding.

Closes #30.