New possibility "Ignore differences lower than" #603

Is your feature request related to a problem? Please describe.
It often happens in the project, that some image url on page changes but the image itself doesn't or similar small differences are detected. In such case, people responsible for accepting have to spend a lot of time accepting screenshots with no visible difference.

Describe the solution you'd like
I think we may implement a new feature that will be taken and described on wiki as something to use only on User (project team) responsibility. This function can be implemented in code and allow user to choose percentage of difference that will be a bottom line to show green status. It means that if you'll put there 1%, then all screenshots that differ 0.1, or 0.5, 0.8% will be ignored and still shown as green (however the difference still may be shown if you open the specific case from the list, but your tests status will be marked as passed). Allow users to choose any percentage number.
To decide whether this should be available for all test suite as global setting or can be specified for chosen url (maybe both options available?).

Describe alternatives you've considered
Additional flag on test report - ignore differences for this page, and specify difference here. Additionally how long should it be ignored with time specification.