ASynK should gracefully deal with vCard parsing issues

[skarra]

Bugs in the vCard file formats on server side should not throw ASynK into a spin. We should handle them gracefully - skipping invalid entries and continue with rest of the stuff.

Want to solve this The Right Way - i.e. the dry-run statistics should themselves include a category 'Errors' (i.e. in addition to New, Modified, etc.) and when there are errors, the sync timestamp will not be updated.