simplify/unify flags concatenation workflows

Implemented changes as suggested in #305 (closed)

• I have some problems figuring out the right way of squeezing flags as suggested in #305 (closed). I left a TODO note in the respective code line (funcs.resampling.concatFlags) and are requesting help from either one of you @palmb / @schaefed . (Or finlly a comprehensive documentation of the many pitfalls of history/flags object handling. I am really a bit lost any time i have to deal with those objects.)

saqc/funcs/resampling.py

@@ -487,7 +487,7 @@ def concatFlags(
         Field name of flags history to append to.
 
     method : {'inverse_fagg', 'inverse_bagg', 'inverse_nagg', 'inverse_fshift', 'inverse_bshift', 'inverse_nshift',
-             'match'}
+             'match'}, default 'match'
         The method used for projection of ``field`` flags onto ``target`` flags. See description above for more details.
 
     freq : {None, str}, default None