Introduce multiple locations for one movie

This pull request will introduce a n-n relationship between the Movie model and Location model.

Now everything which is location related is in the Location class. On top of providing the info for the location an extra comment field exists to further describe it.

For the relationship model I used a ```has_many :through``` and the "association" model (MovieLocationInfo) has also an extra comment field to further describe the context of the usage of that location in the movie scope. Therefore __locations can be shared accross movies, while keeping the possibility to add a comment specific for the movie for that particular location__...

Warning
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I do not know backbone and therefore __with this pull request the UI will not display correctly locations anymore__(even though they exist in the database as separated entities). This should not be complex to fix. 
* The create new movie feature works in the UI.
* The update does not work (even if I doubt you should be able to modify the imdb_id once created...)
* Of course the display in the map do not work