Changed FFmpeg loglevel from "error" back to "fatal" to avoid aborting on recoverable errors

Reverts commit 453b9d8 (from old git repo): https://github.com/bdhero/bdhero-fat/commit/453b9d8cb513d4d156cfe6296287b23906e0add9
Minor/ignore - Use var instead of explicit type for variable declaration in FileUtils.cs
Added TouchFile() method to FileUtils
Minor/ignore - Added MKV abbreviation to ReSharper DotSettings file
Use new TemplateRegistrar class to manage the creation and deletion of temporary files and directories