Allow specific data directories on different target servers

[StevenCTimm]

Currently if one server has a data directory of /data/DAQ/rawdata
and another one has /data/work/data/rawdata, for instance,
then both of those directories must be scanned on all servers, even if they do not exist, putting
all kinds of annoyance error messages in the logs.

Would be nice to be able to configure
server1
directory1
directory2
server2
directory3
directory4