group_concat() does not preserve order of the ORDRE BY rank,
making the ordering quite meaningless for pages inside a file.
The recently introduced combobox to filter on a per file basis
should anyway be prefered than any kind of grouping in queries.
So we just remove the groupings here.
"All files" in the previews tab thus should show the best results
first now, from any files part of the result set.
A GUI option to sort by page instead of rank can be considered.
Purpose is to seperate certain logic from SQLite and generalize it more.
Even though we only have Sqlite atm, in general the database layers
must be stupid as possible, while QSSQuery should do most of the hard work.
Fixes in Tokenizer logic.
Switched to C++17.
Albert S.