Add support for relative paths in playlists, Refactoring, Add testing

Use Library to detect and work on special characters (that includes accents etc.) in playlist files.
Add support for relative paths in playlists, improve support for absolute paths
Major refactoring
Add integration tests with dummy playlist and content files

Fix for special chars in filenames

• executable compiled for Win10 64Bit
• Script runs fully-automatically
• Detects most common special characters -_~+# etc. in filenames and handles them correctly
• Detects most common accented characters äéô etc. in filenames and handles them correctly