22316 - MCO Plugin Packager produces more than one source artifact

In the past when invoking the plugin packager, multiple source artifacts
would be created and multiple builds would be run for every identified
package.

This commit changes the behavior of the plugin packager to only build a
single source artifact and perform a single build.

The ability to keep build artifacts after the build process has
completed successfuly or failed has been added by passing the
--keep-artifacts flag to the packager.

Naming internally to the packager has also been improved. Iteration is
now referred to internally as revision and the --iteration option has
been deprecated in favor --revision.

The #do_quietly?(true|false) method has been renamed to the more sane
 #perform_verbosely(true|false)

The #build_tool? method has also been renamed to #command_available?
22316 - MCO Plugin Packager produces more than one source artifact

Update Changelog
(docs) Change "node reports" to include the word "inventory;" do minor edits

The subcommand name is pretty descriptive, so let's boost its visibility. Via
suggestions from Puppet Labs support team.
22720 - --nodes 'nodefile' doesn't work on ruby 1.9.3

In the past the nodes option failed on ruby 1.9.3 because the input
value was replacing the discovery_options array with a string.

This commit appends the input value to the discovery_options array and
adds some additional testing for the Optionparser class.