Added methods to write VULCAN-required header. Refs #10182.
Refs #10182. Added documentation.

On branch feature/10182_reduce_vulcan
Changes to be committed:

modified:   ../../Code/Mantid/Framework/DataHandling/src/SaveGSS.cpp
- changed a log level.
modified:   ../../Code/Mantid/Framework/PythonInterface/plugins/algorithms/SaveVulcanGSS.py
- minor changes
new file:   ../../Code/Mantid/docs/source/algorithms/SaveVulcanGSS-v1.rst
- documentation
new file:   UsageData/vdrive_log_bin.dat
- test data