HV-808 Fix Mod11 Algorithm, prepare for HV-809

Fixes HV-808 Mod11 and CPF validation issues
`ModUtil` now only have methods to calculate the Mod10 and Mod11
checksum value.
`ModCheckValidator` is the responsible of convert and validate the check
digit
`CPFValidatorTest`  removed useless comments.
`ModUtilTest` Changed assertTrue for assertEquals for better error
report, removed useless comments and messages.