UI - Make more evident the icon that indicates an already added image to a collection

[Vittorio2015]

As a user who has added images from the Image Library to a collection
I want to see the icon next to the images that have been already added to the collection in a different color from the other icons (such as 'Add to Collection')
So that I can clearly distinguish in the Image Library the images that have been already added from the others

Acceptance Criteria

• Use the button class 'btn btn-success' for the icons that indicate an already added image
• Eliminate the 'disabled' class so that the color is not faded, rather full color.

Example

Definition of Done

• Check into version control
• Code review
• Unit/Regression Tests
• Passes continuous integration tests (automation via Travis)
• Meets acceptance criteria

[arthurian]

@brandonATG and I discussed this today and we're adding to the backlog for the next sprint.