Support both "%s" and "{param_name}" in validation error messages

In the "kValidator::GetErrorMsg" method, when "$params" (error message params) array:

• when error message contains "%" that is followed by non-whitespace symbol we execute old code (get from SVN), where "sprintf" was used
• otherwise execute current code with " {param_name}" replacement

At the end both approach should work, since we're not planning to deprecate "%s" approach in error messages.