Fix #100: Add Project URL & Display

### Add-on to Project URL foundation by @nburkley in #161, which: 
- Added URL column to projects
- Added URL (Website) field to projects form and projects admin
- Set Project name to link to project URL if present

![screen shot 2014-01-21 at 10 40 45 pm](https://f.cloud.github.com/assets/85859/1968555/baf3118a-82e4-11e3-9e36-f9c86ba1ca82.png)

### 1 - Display project URL along with web icon on individual project pages
![codemontage-4](https://f.cloud.github.com/assets/226228/2059652/6871e754-8bc4-11e3-8f81-b94d70c5d750.png)

### 2 - Link away to URL from admin projects dashboard
![projects___code_montage-4](https://f.cloud.github.com/assets/226228/2059676/b191ac2e-8bc6-11e3-885e-65dc570ced0e.png)

### 3 - Link away to URL from admin project pages
![codecombat___code_montage-4](https://f.cloud.github.com/assets/226228/2059696/31e86654-8bc9-11e3-9087-2679299b5174.png)
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