Add synonym column to annotation property template

[cthoyt]

Closes #155

This PR adds a new column to the annotation properties template TSV such that synonyms can be added to synonym type labels (because yo dawg, I heard you like synonyms)

It demonstrates by adding INN as an exact synonym of International Nonproproprietary Name.

CC @matentzn I am not sure how to test updates to this file myself, nor where to look for such documentation

[matentzn]

Just so you get this out of the way: do you want to add narrow and broad synonym columns as well?

[cthoyt]

@matentzn I don't think so, we still need to have a discussion about the acronyms and also potentially hierarchical synonym types (#151) before we might need those

[matentzn]

Ok! Thank you!