public boolean isInitialised() {
        return isInitialised;
    }
@return The value, initialising it if required. If initialisation
is required synchronisation will be used to ensure the supplier is only
called once.
Use this method if supplier is not idempotent, has side effects or is
costly to run.
stroom-util/src/main/java/stroom/util/concurrent/LazyBoolean.java