Update icons

I've updated some icons:

- Added file icon
- changed content page icon, since it was the file icon
- enabled event icon for p.a.event dexterity event
- added icon for collections
- added icons for ftw.shop (supplier, shop category, shop item)

New icons:
![types](https://f.cloud.github.com/assets/7469/1832231/e6196ce8-73ac-11e3-9291-8cdc95542e9f.png)

@ninfaj could you take a look, please?