Feature Request: Customizable Toolbar

[h5aaimtron]

I'm using version 2.5.2 and it is pretty decent overall, however; there are a few things that I could see make this even better. The biggest one would be the ability to add controls to the toolbar (.lb-dataContainer) div. The reason for this is that I would love to replace the download button (CORS issues) as well as add some controls that add functionality that I'm looking for specifically. What I suspect could happen is have an array of controls backed by a common class with properties like type, title, icon (if any), position (left or right), and a call back or subject to subscribe to when the control changes. Alternatively for the download specific issue, you could modify the image model to have a download url that could be provided, but the controls additions would be awesome.