New rule for empty statements

[ans-bar-bm]

Related discussion: #716

If there is further discussion needed / you do not want this rule please feel free to tell me / close this; i just had it implemented locally and figured may as well put it up as a PR here.

Currently reports a warning for all empty statements besides:

• "if guards"
  if Customer.Get('10000') then; // <- empty, but avoids a runtime error
• empty case lines

case EnumValue of 
    SomeEnum::First:
        ; // <- empty, but does not fall in else part
    SomeEnum::Second:
        Message('Some message.');
    else
        Error('Some error.');
end;

Not sure about any additional special cases, if you know any please feel free to add them / tell me.

Also not sure about all the necessary parts/steps for a new rule, i looked at a previous PR and copied from there.
If there is anything missing or something left to do i can help with please let me know.

[Arthurvdv]

Thank you for contributing this rule, this is a great rule to have in the LinterCop!

I've taken the liberty to renumber this from 0068 to 0069 and increase the default severity from Warning to Info. Personally I'm going to set this to Warning in our own pipelines, but I'm a bit hesitated to set this as the default where it could possible break other pipelines out there. At the moment I use the rule of thumb that new rules only get a default severity set to Warning if the impact is high, for example in the case of a runtime error.