remove duplicates from KEGG annotation files

[colinbrislawn]

When exporting Kegg_Carbon.xls from IMG, I included both carbon and nitrogen KEGGs. While this duplication does not change the results, it's confusing and unneeded; enriched functions appear twice on the bar graphs.

• Rename Kegg_Carbon.xls to Kegg_Carbon_and_Nitrogen.xls and update RMD to match.