Ripple calc

* New uint160 tagged type NodeID.
* Categorize *all* non-generic instances of uint160 as Account, Currency or NodeID.
* Move conversions to and from strings to central .h file.
* Extract macro constants to be functions.
* Get rid of constructors and comparators between tagged uint types.
* New base_uint::copyFrom() allows explicit copying between any uint types
  of the same size.
* And lots of incidental cleaning and removal of unused code.
I was not directly commenting on that part of the code, more towards @nbougalis' comment of renaming ACCOUNT_ONE - after all, even "ACCOUNT_ONE" is just a hardcoded "magic value" indicating that this value should have been left out/not displayed in the first place.