Desktop: create new custom TextEdit widget for notes-field

Currently, the notes field uses a QTextEdit, which doesn't
send a signal if it goes out of focus.  But for undo of
dive-editing we don't want to create an undo object for
*every* text change.

Thus, create a custom TextEdit widget that derives from
QTextEdit and turns the focusOutEvent into a editingFinished
signal.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/textedit.cpp

@@ -0,0 +1,7 @@
+#include "textedit.h"
+
+void TextEdit::focusOutEvent(QFocusEvent *ev)
+{
+	QTextEdit::focusOutEvent(ev);
+	emit editingFinished();
+}