Commands with excess parameters should be parsed incorrectly

[Zhiyuan-Amos]

Commands that do not require any parameters such as HelpCommand and ClearCommand will be parsed correctly even though the user input contains additional parameters e.g help 3, clear lalala.

As mentioned below, we should implement 'execute with warning' instead of 'reject'.

[damithc]

Once we have the undo implemented, even destructive commands such as clear can be executed without the fear of irreversible damage, which means 'execute with warning' gives a better UX than 'reject' for cases like these.