Bug fixes

Changes since 7.x-2.4:

Fixed a bug in getGraphNodeWithNeighbourhood that was occurring when the source entity matched the stop criteria. Fixed the way maxDepth is passed down.

- Rewrote the module with more robust code.
- Derivatives images generated are now optimized.
- A configuration form has been added in the admin : it is now possible to select exactly an optimizer for each supported mime type (the priority system is gone) and to edit the optimizers options.

BC break : The OptimizerInterface was modified.

Issue #2955404 Mixed Content Error
Issue #2990417 Incorrect variable name on configuration
Issue #2986821 Skimlinks API changed. Removed form validation.

Bug Fix #2999681 Captcha Keypad module not effective against robots