Making adding images to collection easier

At the moment, adding images to a collection is rather cumbersome, which discourages people from doing it.

It involves clicking on the "..." menu, select "save", wait for the list of collections to come up (which takes a few seconds), scan through the list to select the collection, and finally click on "save". Adding an image can take 4 clicks and 5-10 seconds.

Ideally, it should be a simple drag and drop operation, with the list of collection on a sidebar.

But that's probably quite a bit of work and reorganization of the pages, so I am proposing something that can be implemented more easily.

At the moment, the site already has the interface for people to add images to a contest collection. People just have to click on the (+) button in the contest page, and then select a list of images from their library to add to the collection.

So I propose that the same code be reused for any listing of images, such as the main collection of images, people's profile page images, etc. Right now we have two dropdown menus, one for sorting ("Most Reaction", etc.), and one for filtering. So just add another dropdown menu "Collection" that shows a list of collections.

Once user click on that dropdown list and selected the collection, a checkbox is added to every image shown. There is also a "Save" button. The operation is just the same as when people add images to a contest collection.