ACCUMULO-2616 Bump maven plugin/parent POM versions

Change Apache parent POM to version 14. Drop resulting redundant and/or
unnecessary plugin versions, configuration, and properties.

Update bouncycastle test dependency version and incorporate into the
dependencyManagement section and fix resulting deprecation warnings.

Drop redundant m2e container in assembly POM. Migrate to non-deprecated
surefire/failsafe fork settings. Update other plugin versions to latest.
Merge branch '1.6.0-SNAPSHOT'