Created Pgsql::Transaction class for handling of transactions. It auto rollsback if no commit has been done.

Also moved some code out of the connection files to their own files.

pgsql/Pgsql_Canceller.h

@@ -0,0 +1,28 @@
+#ifndef PGSQL_CANCELLER_H
+#define PGSQL_CANCELLER_H
+
+#include <string>
+#include <libpq-fe.h>
+
+namespace Pgsql {
+
+	/** \brief Wrapper for a cancel object from libpq.
+	 */
+	class Canceller {
+	public:
+		Canceller() = default;
+		Canceller(PGcancel *c);
+		Canceller(const Canceller&) = delete;
+		Canceller& operator=(const Canceller&) = delete;
+		Canceller(Canceller&& rhs);
+		Canceller& operator=(Canceller&& rhs);
+		~Canceller();
+
+		bool cancel(std::string *error);
+	private:
+		PGcancel *m_cancel = nullptr;
+	};
+
+}
+
+#endif // PGSQL_CANCELLER_H