This reverts commit b1c0a7cd.

The plugin publishing process has moved to a new plugin-based approach
that brings with it some significant limitations:

 - There's no staging to allow the promotion of good release builds
 - There's no easy way to upload an existing artifact
 - There's no control over the published pom.

The risk brought by these limitations, particularly the first, are
too great so we will no be publishing the Boot plugin to the Portal
until they're resolved.

Changing the plugin's ID was a breaking change that would require
users to do some work when they upgrade to Boot 1.3. The ID of the
plugin was changed purely so that it met the Portal's requirements.
Given that the plugin will not be published to the Portal for the
foreseaable future there's no need for us to inflict a breaking change
on people when there will be no benefit.

See gh-1567