feature/456: weights added, listing page recreated

* Weights has been added for the 'Walkhub key feature' content type.
* Listing view (and block) has been modified for ordering items based on the weights.
* List's block view got a custom template for showing 2x4 features on desktop and 4x2 features on mobile screen properly aligned.
feature/456: CSS run with gulp

In addition corrected the package.json file
Merge pull request #59 from csanyiarpad/feature/456-walkhub-features-content-type

feature/456: weights added, listing page recreated