Allow specification of multiple datatypes_conf.xml files.
If there are conflicting datatype registrations - the registration that appears last in these files will be used. There is an open issue here regarding order of sniffers. This is going to just piggy back on whatever the tool shed would do - so however we decide for instance to resolve sniffer orders in that respect will work with this mechanism as well.

For now though - lets just specify that the best practice should be to just place all non-shed sniffers in one file if specifing multiple datatypes configurations manually like this.