SW-9344 - Refactor Media backend controller
SW-9344 - Refactor ThumbnailGenerateCommand to be fault tolerant
SW-9344 - Include keep Proportions flag in interface
SW-9344 - Refactor basic thumbnail generator
SW-9344 - Refactor Thumbnail Manager
SW-9344 - Refactor Media Model
Merge pull request #1494 in SW/shopware from bugfix/master/sw-9344-media-manager-changes to master

* commit '387473dc1b57d5f464293f16f75f61d3ddbd684b':
  SW-9344 - Refactor Media Model
  SW-9344 - Refactor Thumbnail Manager
  SW-9344 - Refactor basic thumbnail generator
  SW-9344 - Include keep Proportions flag in interface
  SW-9344 - Refactor ThumbnailGenerateCommand to be fault tolerant
  SW-9344 - Refactor Media backend controller