Added new fields to be set by the backend when building a response: contentsUrl, thumbnailUrlList, thumbnailWidthList, thumbnailHeightList, entityRef
Merge pull request #877 from jtorrente/contentURl_in_repoelement

Added new fields to be set by the backend when building a response: cont...
wip - repoGallery/tileButton/Infobutton
wip Skin out of ApAssets
wip RepoWorker/RepoGallery
wip ExtendedSkin
wip RepoView/DownloadFileWorker/Refactoring