Use constants instead of arbitrary ints in the code

[mgrundkoetter]

In the class In2code\Powermail\Domain\Validator\InputValidator in isValidFieldInStringValidation some "random" ints are used to identify the validator. This is bad style from a static analysis point of view and should be replaced by public constants in this class which can then also be used in derived classes.

[mschwemer]

Thanks. This is correct :-)

We plan to introduce static analysis in the next weeks for powermail and will consider it to improve the situation here.