JS Tests: Refactored config handling.

Still far from perfect, but better than it was.

test/config-example.js

@@ -7,11 +7,13 @@ var testconfig  = require("./testconfig.js");
 
 exports.accounts = testconfig.accounts;
 
-// Where to find the binary.
-exports.rippled = path.resolve("build/rippled");
-
 exports.server_default  = "alpha";
 
+exports.default_server_config = {
+  // Where to find the binary.
+  rippled_path: path.resolve(__dirname, "../build/rippled")
+};
+
 //
 // Configuration for servers.
 //