Export cover summaries over aux. meta

[beijbom]

Add functionality so output is similar to CPCe's summary sheet - 1) data reported by transect, with an overall mean also provided; 2) summary data for major categories provided (eg. coral, inverts, soft seds, etc) as well as for detailed sub-labels (eg. for each species of coral); 3) Data output in both Percent and Point format in same file.

Users need to be able to choose which meta-data field to aggregate over.