Filewriter should be able to construct the filenames

Created by: mattclarke

Currently NICOS tells the filewriter the name of the file to save and where to save it.

The filewriter should also contain the optional logic for constructing the filename and path based on information from NICOS (or another client).

• The root directory should be set using the filewriter config.ini (already implemented)
• NICOS gives a base path and filename via Kafka (e.g. SOME_PATH/SOMEFILE)
• When run the filewriter creates a file based on the supplied filepath with a sequential number in the root directory (e.g. SOME_PATH/SOMEFILE01.NXS, next run would be SOME_PATH/SOMEFILE02.NXS)
• The filepath and last number are stored in Kafka so the filewriter can retrieve them if it is restarted