Resize sidebars using mouse

[reckart]

Is your feature request related to a problem? Please describe. The sidebars of the annotation page can be resized, but only by going through the annotation preferences dialog.

Describe the solution you'd like It would be nice if there were dividers on the page that could be dragged using the mouse, similar to the divider that separates the curator's view from the annotator's views on the curation page.