correct anchor pattern bug number

`driftfile` [String]: Allows the setting of the driftfile location.
`keys_enable` [Boolean]: Should the ntp keys option be enabled?
`keys_file` [String]: Where are the keys stored?
`keys_trusted` [Array]: List of keys to trust.
`keys_requestkey` [String]: Request key to use.
`keys_controlkey` [String]: Control key to use.

If keys_enable is set then the directory that keysfile is stored in is
created (recursively).  Currently we don't manage the keys file but that
is an option to be added.

Add a single ntp.conf.erb as the standard template going forward,
to ease the maintenance burden of adding features to this module.

This adds:

`preferred_servers` [Array]: The servers to prefer.

As requested by Erik Dalén!

We're following (where possible) the pattern of having parameters only
exist on interface classes.  As ntp::config and ntp::install are just
internal, private, classes, these don't make sense to allow changes to.

A lot of changes here, primarily to unify the spec testing in a single
spec file to reflect the changes to the private ntp::config and
::install classes.  As a side effect make sure we properly test each
supported distribution (including Gentoo properly) and prefer to use
'content' => /blah/ rather than other methods of testing file contents.

Merge all the templates together, add a few new features to help with the merge.

Instead of a boolean with hardcoded values we now just convert
restrict into an array of lines related to restrictions.

Convert restrict to an array of restrictions.

Add specs for restrict.

2.0-rc1 release.