code: public static <T1, T2, R> BiFunction<T1, T2, R> softenBiFunction(final CheckedBiFunction<T1, T2, R> fn) {
          return (t1, t2) -> {
              try {
                  return fn.apply(t1, t2);
              } catch (final Throwable e) {
                  throw throwSoftenedException(e);
              }
          };
      }
docs: Soften a CheckedBiFunction that can throw Checked Exceptions to a standard BiFunction that can also throw Checked Exceptions (without declaring them)
  
  
  <pre>
  {@code
  
  
  ExceptionSoftener.softenBiFunction(this::loadDir).applyHKT(".core","/tmp/dir");
  
  public String loadDir(String fileExt,String dir) throws IOException
  
  }
  </pre>
  @param fn CheckedBiLongFunction to be converted to a standard BiFunction
  @return BiFunction that can throw checked Exceptions