easier export/backup and import for manual contact infos

[bernhardreiter]

Using sql commands when exporting manual contacts has the drawback
that the specific _ids for interlinking the table entries have to be considered.
This makes it complicated to create script that exports and re-imports parts of the manual
contact infos, e.g. 100 contacts out of 300.

technical ideas

fody-backend has the ability to return and insert contact entries based on a datastructure
that views one entry from the perspective of an "organisation" and offers a traversed tree as
a json object. This works without "internal ids".

The idea is to build upon this interface for the purpose of backuping and re-inserting bulks.