Fix improper localization in one file, and migrate the other two to the more recent version.
Since we are using ARC, we don’t need to set Objective-C objects to nil.
The sole exception is the plug-in handling code in PlayerPROCore, which isn’t ARC on 32-bit.

Make the Music List Object class implement the NSCoding protocol, for future use.
Merge branch 'master' into PPK-overhaul