Add new rule: Methods should not be empty

[fabriciocolombo]

There are several reasons for a method not to have a method body:

• It is an unintentional omission, and should be fixed to prevent an unexpected behavior in production.
• It is not yet, or never will be, supported. In this case an [ENotImplemented|ENotSupportedException] should be raised.
• The method is an intentionally-blank override. In this case a nested comment should explain the reason for the blank override.

Exception
An abstract class' may have empty methods, in order to provide default implementations for child classes.

[Teloah]

Isn't this already kind of covered by "Empty 'begin' statement" rule? I see a lot of those violations, because I quite heavily use Null Object Pattern and, naturally, have a lot of empty methods.

[fabriciocolombo]

In a way yes, but empty 'begin' statement is very generic.
Methods should not be empty is more specific.
We'll leave this on hold for now.

[marcosrocha85]

On a past team I worked, we used to just write an "Exit;" statement on virtual procedures that weren't abstract. Just because on Delphi 5 if you override an abstract method and call inherited, the IDE raises an abstract error. Above Delphi 6 that error doesn't appear anymore. So I think that situation should be considered.