Feature/upload prototype

the upload prototype for our app :+1: 

includes the following:
 * /song rest resource
   * GET /song list all songs
   * GET /song/:id get metadata for sing with id
   * GET /song/:id/raw get the song itself for the id
   * POST /song upload a new song (as multipart; key is "file")
 * angularjs site to upload files and list all available files
   * the site can also be used to play the songs

example for a song in json:
```json
{
    "addedDate": "2014-10-31T15:21:23.528Z",
    "title": "I Don't Want To Be Here Anymor",
    "artist": "Rise Against",
    "album": "The Black Market",
    "year": "2014",
    "comment": "",
    "track": 2,
    "genre": 17,
    "file_id": "5453a8f33da9622806fb3520",
    "_id": "5453a8f3cd412e280614e9d1"
}
```
We should add i18n and message bundle support here. TODO for later.