Rename pmx_helper spec to match implementation filename.
Allow optional customization of displayError JS helper.

I need to render one of these templates with a different style in a
different location for some deployment changes I'm making. I also need a
link in the message.
Add JSON response to metadata refresh endpoint.

This will be used in a target health check on deployment.
Check target status before allowing a deployment.
Refactor PMX.displayError to use default options.

The shared/notice template is only ever rendered by handlebars via this
helper, so changes to the markup should not affect anything in the
browser because we are still displaying the same compiled markup in the
end.
Merge pull request #469 from CenturyLinkLabs/feature/enable-deployment-on-health-check

Enable deployment after health check
Merge pull request #468 from CenturyLinkLabs/chore/add-capability-to-display-error-helper

Add capability to display error helper