Add restore from csv backup functionality #93
Description
With the functionality of #4 it is possible to dump all counters into a csv file. However, it is not yet possible to import counters from such a csv file (or I have missed that, then I am sorry).
I can also make an attempt of implementing this if you like. Some thoughts I have:
- All entries of the import csv file are added to the list of counters, so already existing counters keep existing.
- What should happen if an already existing counter has the same name as a counter of the import csv file? Maybe skip the redundant counters during import and print a warning afterwards that they were skipped.