content ratings on detail page to new mocks/icons (bug 931947)

(Aiming for 12/17)

[Mock](https://bug931947.bugzilla.mozilla.org/attachment.cgi?id=8344778)

[New icons](https://www.globalratings.com/download_library-mozilla.aspx)

[ESRB Storefront Guidelines](https://bug928587.bugzilla.mozilla.org/attachment.cgi?id=820731)

**Notes**:

- rightfully switch from ```background-imgs``` to ```img```, with mapping from slugs to img srcs in ```settings.js```
- content descriptors in text next to content rating icon 
- new PEGI/Generic icons, use CLASSIND icons rather than building our own via CSS
- scale icons down to 48px width
- PEGI shows descriptors icons on the right, other bodies show interactive elements (PEGI's interactive elements are in the form of descriptors)
- less hard-coding PEGI stuff

## Non-PEGI Desktop + Mobile

![screen shot 2013-12-10 at 11 31 45 am](https://f.cloud.github.com/assets/674727/1717704/314ce37a-61d3-11e3-9af2-3c852648baba.png)

![screen shot 2013-12-10 at 10 40 51 am](https://f.cloud.github.com/assets/674727/1717706/392bbb3e-61d3-11e3-905b-b2c2f16bf446.png)

## PEGI Desktop + Mobile

![screen shot 2013-12-10 at 11 33 43 am](https://f.cloud.github.com/assets/674727/1717710/42132962-61d3-11e3-8ed8-41c3df457ac0.png)

![screen shot 2013-12-10 at 11 33 46 am](https://f.cloud.github.com/assets/674727/1717701/2a1cce3a-61d3-11e3-9231-713e4d6f0619.png)