Apple today announced that it has signed agreements with all the major music labels to offer their music in a DRM-free format on the iTunes Store. Like prior iTunes Plus tracks, all music will now be sold in DRM-free, 256kbps AAC format. Starting today, eight million songs are available; all ten million songs are expected to be available DRM-free by the end of the quarter. iTunes will offer customers a simple, one-click option to easily upgrade their…