still not working: Add something to playlist

(debug left in place. when you run into a crash please not the console info so we can investigate)

* ask for the name of the new node through the interaction framework (node creation runs in a separate thread now to avoid interface blocking)

* don't fail http output if AVAHI support is enabled, but the avahi daemon is not running. Just generate an error and continue.

* update of the German translation by Mathias C. Berens | welcome-soft with some few additions by myself

What is currently broken:
 * Some playlist demuxers (shout, dvb and pls)
 * DAAP
 * BeOS playlist
 * GPE playlist, I suppose

What has some trouble:
 * Meta handling in several demuxers (most notably TS)
 * Skins2 playlist (doesn't refresh correctly)
 * OS X playlist (see bigben's latest commits)

keyboard shortcut is used to toggle pause instead of a skin button)

* forgot to add UserOkayCancel to the header (creates the same dialogue as UserYesNo, but with different labels)

* the core is widget-free now (except for the header to keep wx compiling, hopefully)
* updated the OSX-implementation to reflect the recent changes

more clean up is necessary; testing and any feedback is welcomed

refs #553

* introduction of a widget-free progress bar dialogue, partially already committed in [15617] (core and OSX only, refs #553)