Introduce UtilT::ListDifference with equals parameter

for lists of arbitrary types. This can even cover case-insensitive
QString comparations.
Added BookmarkManager ExtraInfo tables and set/retrieve functions
Initial extra info set/retrieve and UI in BMEditDlg

UI doesn't have code.
Set/retrieve is done using lists, but i think we'll switch to Qt models
for extra infos instead.
Add BookmarkExtraInfo retrieve/update by model funcions

Also beiidx is used for model now.
BMEditDlg now uses model based BookmarkExtraInfo for its UI.
Introduce BookmarkExtraInfoAddEditDialog
Implement extra info adding in BMEditDialog
Fix extra info record adding
Implement extra info removing in BMEditDialog
Try to set item delegate for bookmark extra info type in BMEditDlg
previous attempt failed, switch to normal item delegate method for it.
Now shows correct type names in display mode too.

Switched to QStyledItemDelegate which provides a convenience function
'displayText()' instead of QItemDelegate! Lack of discoverability of
this feature but anyway thanks Qt!
Converted BMViewDlg's text editor to a rich text edit

BUT still we show the descriptions as plain text.
Show bookmark extra info in BMViewDlg
HTML-Escape the property names and values in BMViewDlg

in addition, make the table and the "Value" cell fill all space.