TBytesHelper cleanups - LoadFromStream block and CalculateCRC32

[bogdanpolak]

• I wanto to enable loading bytes from a stream into a TBytes, but only portion of stored data. Add: length to LoadFromStream.
• I want to calculate CRC32 check sum of the whole TBytes content by default. Existing method GetSectorCRC32 is expecting a start index and a length. I wont to rename method to calculateCRC32 and allow to call it without parametrs

procedure LoadFromStream(const aStream: TStream; const aLength: integer);
// before: procedure LoadFromStream(const aStream: TStream);

function CalculateCRC32(aIndex: Integer = 0; aLength: Integer = 0): LongWord;
// before: function GetSectorCRC32(aIndex: Integer; aLength: Integer): LongWord;