Create Tiered Sponsorship Structure and Content About Donation Process

### Problem

We've been taking on a lot of sponsors to the public site in recent weeks and in doing so, the page is getting fairly long. Currently, we don't have any sort of ordering methodology - we just haphazardly order in a semi-cronological ordering with a few exceptions (RIT, AT&T, etc.). This leads to donors who have given more in recent years potentially being recognized toward the bottom of the page.

### Solution
- Develop a tiered donation structure where we take account of the monetary value of each donation (even if it comes in hardware/software/license form) and pool the donors into 3 groups according to what they've donated:
- Platinum: This is the highest possible group and is there for large donors
- Gold: This is for our medium donors
- Silver: This is for donors that give one-offs or smaller donations. We still want to give them a group that sounds appealing so they know they're being recognized.
- Only show Platinum/Gold donors in the rotating collection on the homepage.
- We decide on the monetary value ranges for each of these groups based on our knowledge of donation values over the past few years.
- We change the public site sponsors page to order these groups in three sections, with Platinum at the top of the page (rough concept):
- We move the Sponsors page to it's own dedicated tab as a dropdown. We keep the current page, and also add a page about how to donate and the donation tiers.
- The 'how to donate' page should express what we do with the funds (projects, equipment, etc.), explain RIT's donation process, and the tax-deducibility of donations (i.e. that we operate as a non-profit)
- We inform companies that visit about our ability to take donations and why it is great to benefit the organization.

cc @mbillow @com6056

This is an enhancement of https://github.com/ComputerScienceHouse/CSHPublicSite/issues/43.

Inizia individuando la pagina pubblica degli sponsor, la rotazione degli sponsor nella homepage e la navigazione del sito. Esamina come sono attualmente organizzate le voci e le pagine degli sponsor, quindi definisci gli intervalli dei livelli e le informazioni sulle donazioni prima di fare in modo che le sezioni degli sponsor, il menu a discesa e la pagina delle donazioni corrispondano alla struttura richiesta. Il lavoro sarà completo quando il sito presenterà sponsor suddivisi per livello, mostrerà solo Platinum e Gold nella homepage e spiegherà il processo di donazione e l’utilizzo dei fondi.

Scritto dal modello di indicizzazione a partire dal testo della issue.