in JSON writer, extra NL at end of mapping & array - maybe makes layout look better (experiment)
lose inappropriate old RequireNotNull() on String class in FileExists(cuz changed API)
minor tweaks to JSON writer file termination (always end in LF) and regtests
fixed bug with (new optimized for Seekable) BinaryInputStream::ReadAll() for case of empty stream
Added regression test case for reading empty JSON - should get back badformatexception
www.fightrice.com/mirrors/apac... mirror failed for xerces - so hooked in a differnt one