This mostly reverts commit 37de4458.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Fix the bug where caching would stay all the time when stopping

Jamendo radios are accessed trough the demuxer, otherwise the SD script will be too slow.
The demuxer should also resolve all the Jamendo api calls to the track unit, xml only.

It closes #2272 and #3350.

This patch
    - uses owner/owned windows so that all skins2 windows get
    minimized at the same time
    - add WS_MINIMIZEBOX to enable minimize in taskbar button
    - some cosmetic