Added the capability to reset the password manager

Also some documentation about the password manager.

pglab/ConnectionListModel.h

@@ -59,6 +59,7 @@ public:
 	/** Save changed config, group is not allowed to change
 	 */
 	void save(const ConnectionConfig &cc);
+    void clearAllPasswords();
 	/// Create a new group in the DB and place in the tree
 	std::variant<int, QSqlError> addGroup(const QString &group_name);
 	std::optional<QSqlError> removeGroup(int row);