Feature request: Chunked backup archives

Agenda:
Some shared hostings limit the filesize for new files. I.e. strato.de limits the filesize to 64MB.
It results BackWPup to freeze and endlessly retry to create an archive if it exceeds 64MB.
Splitting the job to some smaller ones doesn’t help if the site is big. In some cases even the smallest possible job still exceeds 64MB.

Solution:
Add option to create chunked archives with limited filesize.

Some help:
Workaround from this article could help to implement the feature:
https://stackoverflow.com/questions/26000277/php-fwrite-file-leads-to-internal-server-error