Woofer player v1.4.0 Pre-release 2

Changes against v1.4.0-pre1:

• fixed downloading pre-release update even though Stable update channel was selected
• fixed error when updater launched Woofer from woofer_update directory and then Woofer tried to delete woofer_update dir during downloader init
• media adding stopped immediately, woofer now handle new media adding event when some media adding is already being processed
• save and load playlist menu items hidden
• inactive updater setting hidden