Updated description.

- Removed references to specific version (ie. "2014")
- Added note regarding no cleanup/removal of previous version(s)
Updated AutoPkg MinimumVersion to 0.4.1
Updated RELEASE_YEAR to 2015
Minor tweak to UrlTextSearcher re_pattern
Cleaned up pkginfo section

- Removed the unattended_install/uninstall as they were not good
  choices for general use outside my lab.
- Set minimum_os_version to reflect requirements for SketchUp
  Pro 2015.
Re-enabled and updated CodeSignatureVerifier

- Removed comments from around CodeSignatureVerifier processors
  now that SketchUp Pro 2015 codesigning adheres to current
  standards.
- Switched from 'expected_authority_names' to 'requirement'
Updated minimum_os_version

- Apparently the requirements on SU web site, albeit apparently
  references v2015 specifically, are wrong. The *.app bundles
  themselves specify LSMinimumSystemVersion as 10.8. So, go
  figure.