msr2data becomes more tolerant

Non-existing msr-files in the specified list of runs are now ignored as far as possible!
Still a warning for each non-existing file will be issued!
Before, encountering such a file led to the termination of the program.

Also the writing of the empty lines at the end of the data-output-file should be fixed now in this case.
It is needed to get a "correct db-file".
Before, when the program has been aborted before the last run was processed, these empty lines had not been appended to the file.

src/include/PMsr2Data.h

@@ -93,6 +93,7 @@ class PMsr2Data
     mutable unsigned int fNumSpecParam;
     mutable unsigned int fNumTempRunBlocks;
     mutable unsigned int fRunNumberDigits;
+    mutable bool fHeaderWritten;
 };