Implement a findByIDs method

[sdeleuze]

In order to improve performances in higly distributed platform (avoir N call to findById)
To be implemented at service and controler level

[bmeurant]

PR #132 resolves this issue.

findByIds API:

/api/albums?ids[]=2&ids[]=3:

[
    {
        "id": 2,
        "title": "Somewhere Within the Shadows",
        "publicationDate": "2000-11-01",
        "number": 1,
        "coverName": "blacksad-1.jpg",
        "series": 1
    },
    {
        "id": 3,
        "title": "Arctic-Nation",
        "publicationDate": "2003-03-01",
        "number": 2,
        "coverName": "blacksad-2.jpg",
        "series": 1
    }
]