Figure out how to show sub-projects in landscape

[lgritz]

Changes requested

• [x] Imath should probably be in the "math foundations".
• [x] Language Interop should not (maybe in software foundation?).
• [ ] OpenRV should have a big logo because it's an ASWF project.
• [x] DPEL should be in scenes & geometry, not review.
• [x] OSL is adopted, not incubating

[jmertic]

Howdy - I've fixed most of these with #916

Two outstanding:

• I will make the OSL change in PCC, which will update the landscape overnight.
• Large logo for OpenRV