Complete iPod collection rewrite (also supports iPad, iPhone)

This is a result of 3-month effort to make Amarok iPod-like device
support future-proof and less buggy by using more modern MemoryMeta
framework to manage tracks internally.

The new plugin still uses libgpod [1] to access the devices and
supports all devices supported by it. The newest models may need the
infamous libashab.so library.

FEATURES:
 * Small configuration dialog for iPods that shows troubleshooting information
   and allows to change iPod name.
 * Improved usability of iPod playlists: iPod collection automatically transfers
   tracks dropped to iPod playlists to iPod when it is needed.
 * Tracks can now be transcoded when transferring them to iPod.

CHANGES:
 * optional libgpod dependency raised to 0.8.2 to support newest iPods.
 * Amarok now prevents accidental unmounting of iPods in (small) time-frames
   when iTunes database on iPod is not yet updated.
 * Amarok detects when iPod is to be ejected from system and gracefully
   disconnects it when it occurs.
 * Hitting the eject button on iPod collection ejects it also from the system.
 * iPod collection now detects whether iPod is safe to write and marks iPod
   as read-only if not. This prevents "iPod shows 0 tracks" problem.
 * Correct progress bar advancement when transferring tracks to iPod.
 * iPod Collection supports multiple simultaneous cancellable transfers.
 * Improved dialog to initialize iPod.

BUGFIXES:
 * Detection and elimination of stale and orphaned iPod tracks now works
   correctly; users are notified about these when iPod is plugged in.
 * iPod playlists now work correctly.
 * Show correct error when transferring unsupported files to iPod.

[1] http://www.gtkpod.org/wiki/Libgpod

FEATURE: 291722
FEATURE: 139454
FEATURE: 219963
BUG: 279797
BUG: 289304
BUG: 234876
FIXED-IN: 2.6
DIGEST: Amarok's iPod support is completely rewritten fixing many bugs
        and adding features