Updates PlaylistManager to use faster jackson XML serialization.

Removes native xml.bind serialization for improved compatibility with
 Java 9.

 Global optimize imports on the entire project.

.idea/vcs.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="" vcs="Git" />
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
   </component>
 </project>