Add renamer API call for one movie

This update is the second step in implementing https://couchpota.to/forum/thread-1643.html

A new API function is added: renamer.scanfolder which requires as input:
- a folder with the downloaded files (which can be anywhere on the computer, not only in the 'from' folder). The scanner will try to find the release name based on the folder supplied, e.g. if the folder is c:\download\mymovie, it will include mymovie in the indentifier words.
- optionally the movie files. not really sure what the added value of this one is... ;)
- the downloader and download_id. With these it will match to the release so that movie name and quality are known upfront (no need for the .CP tag in this case)

The next step is to call this function internally from the renamer.checksnatched function. For this all downloaders need to be updated to include the folder it was downloaded/unpacked to.