HPCC-9791 XML file spray logging improvement

Add
- splitOffset value log at findSplitPoint() call
- log predicted recordsize, maxRecordSize and blockSize when "End of record
  not found (need to increase maxRecordSize?)" exception occurs
- extension to exception message with same info as logged (offset, predicted
  recordsize, etc.
- relation between blocksize and maxrecordsize parameter

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>