Make is_set_bit a universal template function
[FOLD] Cleanup of STAmount formatting functions. Remove boost::format
[FOLD] Reduce use of boost::format
[FOLD] Reduce use of boost::format
[FOLD] Reduce use of boost::format
[FOLD] Reduce use of boost::format
Add beast::tagged_integer:

 * Wraps standard integer types to provide type-safety

 * Named types provide self-documenting semantics

 * Catches programmer errors involving mismatched types at compile time

 * Operators restrict mutation to only safe and meaningful operations