Fix COG_Category metadata

COG_Category is now formatted as lists of lists,
so categorize_by_function.py will work properly.

Names of COG categories have been added in addition to just the
single letter COG category code.

Also, the first (highest level) is now one of the 4 groups that the
COG category belong to, so they can be collapsed at both level 1 and 2.

Fix #120
Merge pull request #121 from mlangill/issue120

Fix COG_Category metadata