Update Metrics to 3.0.1

Formerly at 3.0.0-BETA3

This commit also deletes the ${metrics.version} property from the
top-level pom.  This property doesn't seem to be used anymore, and the
properties ${metrics3.version} and ${metrics2.version} are preferred
regardless to avoid confusion about which major version is implied
(Titan depends on both, 3 directly, 2 indirectly).

(cherry picked from commit f56c54c85ee5b465be00afce241de6c0742cce8a)