Feature Request: Filter based on detected type to exclude "share" links

[ssokolow]

Your DownThemAll! and Browser Version and Operating System

DownThemAll: 3.0.5
Firefox: 49.0a2 (2016-08-01)
OS: Lubuntu Linux 14.04

Expected Behavior

DownThemAll should have a way to filter based on whatever source it uses to assign icons to detected links. (This successfully identifies images without catching Pinterest share links)

Actual Behavior

DownThemAll seems to only allow filtering by raw URL matching, which results in false positives for Pinterest share links when you filter for images.

Steps To Reproduce

1. Go to any Tumblr blog which incorporates Pinterest buttons
2. Open DownThemAll's file picker to the links tab
3. Look at how actual images in the list get image icons while Pinterest links do not
4. Try toggling the images filter and look at how both images and Pinterest links get selected/deselected.

Additional info such as log extracts

Because I generally notice this on NSFW blogs, I'd rather not give a log.