PrefixedLocalStorage = function () {
  this.prefix = ''; // Prefix for localStorage keys
  this.param = 'prefixedLocalStorage'; // Param to use in querystrings
}
Supports pseudo-"namespacing" localStorage for a given test
by generating and using a unique prefix for keys. Why trounce on other
tests' localStorage items when you can keep it "separated"?

PrefixedLocalStorageTest: Instantiate in testharness.js tests to generate
  a new unique-ish prefix
PrefixedLocalStorageResource: Instantiate in supporting test resource
  files to use/share a prefix generated by a test.