Fix #632, part 2 (don't cause fatal exception opening pfx-file in central store - also on delete)
Fix #634 (never match certificates by friendlyname*)
Fix #635 (using iissites-target with dns/ftp/webdav-validation broken)
- This will cause some certificates to remain behind in the store after they expire, but will prevent potentially much worse stuff from happening, e.g. linking similarly named sites to the wrong certificate. Thanks to @StefanBCN for figuring this one out.