undeprecate transferFlags and move concatenation functionality

from concatFlags to transferFlags

saqc/funcs/flagtools.py

@@ -347,7 +347,7 @@ class FlagtoolsMixin:
 
         .. doctest:: exampleTransfer
 
-           >>> qc = qc.transferFlags(['a','a'], ['b', 'c'])
+           >>> qc = qc.transferFlags(['a','a'], ['b', 'c'], overwrite=True)
            >>> qc.flags.to_pandas()
                   a      b      c
            0   -inf   -inf   -inf