Ability to customize error messages in u_TestCodeIsValid tag

There is TestCodeIsValid for users, that checks code saved before could do:
1. tell, that code is expired
2. tell, that code is not valid
3. tell, that everything is ok with code.

Problem is that error phrases are hardcoded in this tag and can't be changed.

This tag could be very useful in cases, when you perform various activations by email or something like that and having same error message, that "password reset code is not valid" is not good.