Features/proper player

this PR adds the following:
 * metadata editing for songs
   * server side and client side
   * the client side is prototyped on the upload screen but can be easily integrated into another view
 * the ```owner_id``` is set on song upload
 * the ```/song```-resources check ownership of gridfs objects and songs now
 * ability to redownload covers 
   * useful if you upload a song with wrong metadata and want to get the correct cover later
 * a new sidebar with a proper looking player
 * a queue service that allows you to add, reorder, remove songs
 * drag and drop for this queue
 * a placeholder for a "save playlist" button
 * several smaller cosmetic fixes
 * i removed the ng-boilerplate branding and the google+ button library as well


this PR is not meant to be merged, since there aren't enough tests yet. 
**given that it is feature-complete though, you can use this branch for your own work. any future bugfixes that are likely to arise from testing are only minor and will not create error when merging**

screenshot: https://dl.dropboxusercontent.com/u/80174/songster_pr26.PNG
naming: you check here for objectExistsAndBelongsTo.
You go here directly to the song collection
consider naming it: songExistsAndBelongsTo
Also you could add the owner_id check into the query from the current implementation.
I assume it was added later and is therefor encoded as a seperate if.
Maybe you could add in the else part when the doc was found that you queried for a song with a different UserID => maybe an interesting case that should bascially not happen