[CardDAV] Property groups, e.g. for X-ABLabel, not recognized correctly

[rfc2822]

The Cozy CardDAV server recognizes VCard property groups which are grouped by itemXX. (where XX is an integer number), but not by any other group names.

Steps to reproduce:

1. Upload a VCard with item1.TEL:12345and item1.X-ABLabel:My Phone Number. This will show up as "My Phone Number" in the Web interface.
2. Upload a VCard with customclient1.TEL:12345and customclient1.X-ABLabel:My Phone Number. This phone number will be removed by Cozy and not shown as "My Phone Number", although the semantic value is exactly the same.

Expected behaviour:

1. VCard properties should be grouped by group name, and there should be no assumptions about how those group names look like. They may look like itemXX (especially when coming from iOS/iCloud), but every other group name should be interpreted too.
2. Even if the grouping does not work, customclient1.TEL should not be removed completely. There seems to be something wrong in property group handling.

[clochix]

Thanks for reporting @rfc2822