Allows search by category in /adim/pin/
Fix an error when pin does not exist.

There was an error on http://mypinnings.com/admin/pin/4040 because that pin was deleted. This was fixed to simply show pin does not exists.
Disable button in /admin/input/ to prevent duplicates

The Upload button is disabled on click to prevent the page to submit duplicates.
Randomly suffle the results of category listings

When viewing a category, randomly shuffle the results in order to not show always the exact same items in the exact same order in each view of the same category.
Removes duplicates from the category listing.

Detects if the same item is shown in the category listing twice and does not shows again.
Merge pull request #115 from camilotorresf/fixes

Fixes