DER-84 - Commodity swaps are missing the concept of how much and a price at some point in time

[ElisaKendall]

Signed-off-by: Elisa Kendall ekendall@thematix.com

Description

1. Augmented the definition of a commodity instrument to include the commodity, a quantity of that commodity, and its value as of the execution date of the contract
2. Revised the definition of commodity spot contract, commodity basket constituent, and commodity underlier accordingly

Fixes: #1925 / DER-84

Checklist:

• [x] I'm familiar with the FIBO developer quide. My contribution meets all the requirements described there.
• [x] My contribution follows the principles of best practices for FIBO.
• [x] My changes have been reconciled with latest master and no merge conflicts remain.
• [x] This PR is related to exactly one issue. The issue is referenced by using a GitHub keyword such as "fixes", "closes", or "resolves".
• [x] Hygiene tests have been applied by a PR with "(WIP)" in title.
• [x] The issue has been tested locally using a reasoner (for ontology changes).