bytes: make byteconcat have dynamic type arguments so that we can support Strings, List<int> and BigInteger with the same method

Signed-off-by: Daniel Thomas <drt24@cam.ac.uk>
bytes: make byteconcat take a List<dynamic> as its argument and concat N values

Signed-off-by: Daniel Thomas <drt24@cam.ac.uk>
Add inital NigoriNonce class

Signed-off-by: Daniel Thomas <drt24@cam.ac.uk>