WEB: Improving the sponsors in the web, and adding CZI
- [X] closes #31040

Things addressed here:
- Added CZI as sponsor
- Adding an arbitrary number of sponsor logos in the home (previously the style only worked for 6)
- Adding a `Become a sponsor` section to the sponsors page
- Moving all sponsors to the web yaml, and standardizing how we present them in the sponsors page

![Screenshot at 2020-01-15 16-22-57](https://user-images.githubusercontent.com/10058240/72451690-36211480-37b4-11ea-8564-ff5e421b468f.png)

![Screenshot at 2020-01-15 16-23-32](https://user-images.githubusercontent.com/10058240/72451699-39b49b80-37b4-11ea-99ad-50fabe965d9c.png)
