Webpack background-image: url()

[willdoran]

This pull request makes the following changes:

• Changes layout of video.html to include definition of video provider logo images
• This images were not served by webpack as they were not picked up because they were within the translation string for the video input desc
• This is a patch the background images should be moved to the css class and webpack config should be set to use resolve-url on the css/scss

Test these changes by:

• Add/Edit a Post with a Video field, confirm that Youtube and Vimeo logos appear

Fixes ushahidi/platform# .

Ping @ushahidi/platform

…style in en.json. This is less a bug and more a need of a redesign of the video provider logo layout

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This change is 

[coveralls]

Coverage remained the same at 75.176% when pulling adb870b on hotfix/logo-img-webpack into 806692e on develop.