Fix plugin downgrades and version comparison.
Fix plugin downgrades and version comparison.

Add lots of info log prints to track down versioning and downgrade issues.

Add semver-style version comparisons (instead of string version comparisons).
 * Fix case of '1.16.4' being older than '1.9.0'

Add horrible hack for downgrades
 * When a downgrade is selected, delete the same resources as plugin :delete
  - using copy/paste code :/
 * When a downgrade is selected, and source is unset, set source.
  - otherwise, it uses upgrade center logic to select the newest. Always.
  - Use json from update center to grab url, and sub it to this version.
   + A url split to edit only the version folder might be more robust.

The workaround for version-specified files would be to use the original source cookbook and always set source to the desired source. But without the version fix, this isn't super helpful.

Thoughts:
 * the update-center.json should just be dumped to actual json once.
  + file resource?

epu/epu-cb-jenkins,epu/epu-cb-jenkins,epu/epu-cb-jenkins