Adding support for the Powershell plugin.

See https://wiki.jenkins-ci.org/display/JENKINS/PowerShell+Plugin

Change-Id: I337ea896e358fe456e556a95e22e724fe20cd722
Add PMD publisher

Change-Id: I40320337fec0d1564bb1f4b88b4f7a1aa4f2dfc5
ModuleRegistry now cache entry points group

Cache the group entry point instead of each entry individually.

When I originally introduced entry point caching (4deef9ff) I used to
lookup the name and cache it.  Thus, for we ended up doing a new lookup
for each entry point in an entry point group.

Instead, on first lookup, cache the whole group so further entry point
lookup are cache hits.

Change-Id: Ie93ec793bb18a2dadebe736db4c4d33171ceda27
Flatten attribute for publish plugins

plus move examples to tests

Change-Id: Ia785afe40da81c77abe643f3c788e5d4faefbf5d
Merge "Add PMD publisher"
Merge "Adding support for the Powershell plugin."
Merge "Flatten attribute for publish plugins"
Merge "ModuleRegistry now cache entry points group"