Update Interests to reflect iOS Structure

We want interests to have the structure

`{
"name": "Art",
"categories": [],
"imageName": "art"
}`

and the information hardcoded in PearInterests.txt

**Interests**
```
static let interests: [Interest] = [
Interest(name: "Art", categories: ["painting", "crafts", "embroidery"], imageName: "art"),
Interest(name: "Business", categories: ["entrepreneurship", "finance", "VC"], imageName: "business"),
Interest(name: "Dance", categories: ["urban, hip hop", "ballet", "swing"], imageName: "dance"),
Interest(name: "Design", categories: ["UI/UX", "graphic", "print"], imageName: "design"),
Interest(name: "Fashion", categories: nil, imageName: "fashion"),
Interest(name: "Fitness", categories: ["working out", "outdoors", "basketball"], imageName: "fitness"),
Interest(name: "Food", categories: ["cooking", "eating", "baking"], imageName: "food"),
Interest(name: "Humanities", categories: ["history", "politics"], imageName: "humanities"),
Interest(name: "Music", categories: ["instruments", "producing", "acapella"], imageName: "music"),
Interest(name: "Photography", categories: ["digital", "analog"], imageName: "photography"),
Interest(name: "Reading", categories: nil, imageName: "reading"),
Interest(name: "Sustainability", categories: nil, imageName: "sustainability"),
Interest(name: "Tech", categories: ["programming", "web/app development"], imageName: "tech"),
Interest(name: "Travel", categories: ["road", "trips", "backpacking"], imageName: "travel"),
Interest(name: "TV & Film", categories: nil, imageName: "tv&film")
]
```

**Groups**
```
static let organizations = [
Group(name: "Cornell AppDev", imageName: "appdev"),
Group(name: "The Milstein Program in Technology in Humanity", imageName: "milstein"),
Group(name: "Under Represented User Experience (URUX)", imageName: "urux")
]
```