[#153] Rename unattended_upgrades s/-/_/

It's preferable to use underscores rather than hyphens in class names. Refs:

- http://projects.puppetlabs.com/issues/5268
- http://docs.puppetlabs.com/puppet/3/reference/lang_reserved.html#classes-and-types
[#153] Convert t/f params to bools and validate

Per lint check: http://puppet-lint.com/checks/quoted_booleans/
[#153] Variablise file paths in unattended spec

Reduce some duplication of long file paths.
[#153] Test defaults for some unattended params

For params which have any logic embedded in the template:

- origins
- blacklist
- mail_to
- dl_limit
[#153] Install unattended configs after package

To ensure that the default configs from the package are always overwritten
within a single Puppet run.
[#153] Remove trailing whitespace from spec.