fix the search in comma separated multi-value fields

The values in such a DB field (e.g. email) are separated by
", ", not ",".
show the "no abook found" message also if no results are returned
FS#71 treat Internet as a fallback type for email addresses

If there are multiple type parameters to an email attribute, any
(known) attribute supersedes a possibly present 'internet' type.

Note: 'Internet' is only used if it is actually set in the type
parameter. If no type is available at all, the default type
used is still 'other'.
Merge remote branch 'fork/mstilkerich/master' into dev