NEXUS-5961: Simple plexusplugin plugin

A simple plugin written ol'school using Plexus
that tackles major components and uses them
(to verify plexus injection works).

This plugin solely purpose is to verify
that plexus components are still handled as
expected and DI is supported on them.
NEXUS-5961: Simple IT skeleton
NEXUS-5916: Cleanup of the plugin and IT
NEXUS-5961: Updated js header
NEXUS-5961: Renamed
Merge pull request #173 from sonatype/NEXUS-5961-plexusplugin-plugin

NEXUS-5961: plexusplugin plugin