[WIP] Loading fixtures with Nelmio/Alice

The goal is to be more flexible, to be able to load a bigger and more random catalogue.

- [x] install Nelmio/Alice
- [x] ~~install hautelook/AliceBundle~~ not needed anymore :)
- [x] countries
- [x] exchange rates
- [x] promotions
- [x] users
- [x] product properties
- [x] zones
- [x] product options
- [x] taxation
- [x] shipping
- [x] payment methods
- [x] images 
- [x] taxonomies 
- [x] products
- [x] orders
- [ ] find a way to link taxons to products
- [x] settings
- [x] remove User processor if it works without it
- [x] handle unique SKU and ISBN