Add implicit AND booleans at the end.
This fixes a number of issues in LooqsQuery:
(1) A query like a b c p:(something) would fail, because
a b c get merged into one word. This happens at the end.
lonewords are special and do not become a token immediatly. So previous
logic to add implicit ANDs does not apply.
(2) Negations were also broken with lonewords.
(3) The TokenType enum fields were too narrow to be useful for the bitmask
Independent of that, add support for 'limit:'
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.
