refs https://github.com/TryGhost/Toolbox/issues/523
- We need media file imports. Media handler is one of the pre-processing parts that need to be done during the import process
- Media import handler is handling import files with following extensions: ".mp4",".webm", ".ogv", ".mp3", ".wav", ".ogg", ".m4a"
- The implementation is largely a copy-paste with class syntax adjustments from the "/core/server/data/importer/handles/image.js" module
- There are a lot of code similarities between media and image import handlers. The new "ImporterMedia" class could serve as a generic base class for file-storage-related imports
