Adding public option to song creation

* Public option allows user to decide whether song should be included in the All Songs list
* Adds public boolean to song storage to store user's choice
* Current problems are that the button and label don't line up properly in the menu bar and the button can't be clicked on - only the label responds to clicks.
Reformatting the public button to fit better with the Create Song form

* Changed button to a CSS form button instead of image button
Merge pull request #49 from artfoundry/set-song-public

Set song public