Refactor search queries: Introduced QSSQuery

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.

shared/sqlitesearch.h

@@ -3,34 +3,21 @@
 #include <QSqlDatabase>
 #include <QPair>
 #include "searchresult.h"
-
+#include "token.h"
+#include "../shared/qssquery.h"
 class SqliteSearch
 {
-	class Token
-	{
-	  public:
-		QString key;
-		QString value;
-
-		Token(QString key = "", QString value = "")
-		{
-			this->key = key;
-			this->value = value;
-		}
-	};
 
   public:
 	SqliteSearch(QSqlDatabase &db);
-	QVector<SearchResult> search(const QString &query);
-	static bool checkParanthesis(QString expression);
+	QVector<SearchResult> search(const QSSQuery &query);
 
   private:
 	QSqlDatabase *db;
-	QVector<Token> tokenize(QString expression);
-	QSqlQuery makeSqlQuery(const QVector<Token> &tokens);
-	QString fieldToColumn(QString col);
+	QSqlQuery makeSqlQuery(const QSSQuery &query);
+	QString fieldToColumn(QueryField field);
 	QPair<QString, QVector<QString>> createSql(const Token &token);
-	QString createSortSql(const SqliteSearch::Token &token);
+	QString createSortSql(const QVector<SortCondition> sortConditions);
 };
 
 #endif // SQLITESEARCH_H