Extend requireSameVersions rule to optionally enforce same versions among reactor modules

Currently the rule https://maven.apache.org/enforcer/enforcer-rules/requireSameVersions.html does not support checking versions of the actual Maven modules (but only of contained dependencies and/or plugins). Often it is important that all modules of an aggregator project share a common version (in order to ease/allow releases). I propose to add an additional flag sameModuleVersions which if set to true enforces all modules built from the reactor root share a common version. This should also support CI-friendly versions