Add support for feature annotations

[joewandy]

1. A feature could be assigned multiple annotations (names).
2. Users should be able to select which annotations to use, e.g. KEGG, ChEBI for compound data. before running analysis.
3. Annotations could also be expanded by pulling related terms, e.g. related ChEBI terms that are involved in a reaction.

The codes are somewhat there that could do the above, but they're messy and need to be tidied up.