#33, #34, #56 Various bugfixes and changes in behavior

- Removed precaching completely
- Workaround for MusicBee's insistance of calling GetFile() on folders
- Workaround for MusicBee's opening of last used Folder/File on startup

Changed the default behavior of pre-caching everything to optional, c…

…ontrolled in the Settings window. Bumped version to v2.27