Automerge

If warnings was appeared - dialog with warnings details appeared. Each warning is a separate QTextEdit.

That mechanism is general for UBExportAdaptor and can be simple implemented and used in any import or export adaptor.

A small correction for audio item design... strange, it was good on windows and linux, but works not the same on mac.

Not necessary merge

Improved recognition of song's title.
Some code removed from header.

Undo stack disabled ad scene loading because it is not needed there.