Validation strict mode

Maven 3 currently prints a number of deprecation / best practices warning at the start of the build for things that need to be improved and may not be supported in the future.

These can pass by without being noticed since they are at the start, or be easily ignored. It would be good to have a way to fail the build if they exist.

A command line option --strict is a potential solution, though it would be better to be able to set it permanently (e.g. via MAVEN_OPTS or settings.xml) - so a property might be another alternative. Another possibility is exposing it in a way that an Enforcer rule can be crafted so that it can be set on a per-project basis.