Reportback modal

* Opens modal after user uploads a file
* First pass at modal styles
* Allows user to enter a caption

@weerd @DFurnes 
For both of the above I don't think you need to wrap the `.find(..)` item as a `$()` object. It'll return it as a `$()` object anyhoo. So this should work fine: `this.$cropModal.find("#dosomething-reportback-image-form");`