- reimplement binaryToString:
- it now accepts a Slice and nothing else
- it does not return a std::string but instead a proxy object that implements
operator<< (this should be more efficient, as we do not need to touch the
heap in most cases)
- addapt unit tests
- replace all occurences with the new API
binaryToString(DataBuf&) only calls the C-array version. Unfortunately, its
safety check is flawed, as it only works when start is 0 (probably due to its
conterintuitive interface).
binaryToString(byte*) formats the range (start,start+size) => we have to trimm
size if size + start is larger than the DataBuf's size_
