Add new terms for CMI-PB

[beckyjackson]

Resolves #28

Adds two new top-level classes:

• mixture (CHEBI)
• protein complex (GO)

Adds four new ONTIE terms and seven new PR terms described in #28

A few questions:

Do we want to consider adding a top-level "material entity" to group protein, protein complex, organism, and mixture?

Finally, it looks like we already have two of the pertussis toxin subunits:

• ONTIE:0002950 (pertussis toxin subunit 4)
• ONTIE:0002666 (pertussis toxin subunit 1)

Do we want to deprecate these and replace them with the PR terms that we added?

[jamesaoverton]

Yes to both:

1. please add COB 'material entity' as a parent
2. please deprecate those two ONTIE terms in favour of the PR terms

[beckyjackson]

Done!