fixes bug 785430 - Add a service to add new products

@rhelmer r?

This basically just does what [the documentation](http://socorro.readthedocs.org/en/latest/installation/add-product-release.html) says to do except it makes it possible to kick this off from the middleware.

Once this has been done and you think it's good, I'll add it to the webapp and its admin UI. 
I did so to not muddle things. This new file is about products AND releases. That's why I didn't think it belongs in products.py which is all about products. 
Also, creating new files is cheap and is keeps the individual LOC per file shorter and easier to keep things apart. 
Lastly, we, mozilla, won't actually be using this new service since we get our products and releases from the ftpscraper so by making this little thing its own file it felt like it made less of a complication-impact. 

What do you think? Did I really commit a sin or am I making some sense?