Use new collection for avatars only

lib/fileUpload.js

...s/rocketchat-file-upload/client/lib/FileUploadAmazonS3.js

...ketchat-file-upload/client/lib/FileUploadGoogleStorage.js

...hat-file-upload/server/config/configFileUploadAmazonS3.js

...ile-upload/server/config/configFileUploadGoogleStorage.js

packages/rocketchat-lib/client/models/Avatars.js

packages/rocketchat-lib/package.js

packages/rocketchat-lib/server/models/Avatars.js

packages/rocketchat-lib/server/models/Uploads.coffee

server/methods/setAvatarFromService.js

server/startup/avatar.js