Add PE facts to stdlib

As many PE modules have PE specific functionality, but are deployed to all
nodes, including FOSS nodes, it is valuable to be able to selectively enable
those PE specific functions. These facts allow modules to use the is_pe fact to
determine whether the module should be used or not. The facts include is_pe,
pe_version, pe_major_version, pe_minor_version, and pe_patch_version. For PE
2.6.0 those facts would have values true, 2.6.0, 2, 6, and 0, respectively.
Add spec tests for pe_version facts

This commit adds some basic spec tests for the pe_version facts. There are
basic postitive and negative cases.
(maint) Clear all facts before each example

Without this patch example groups must explicitly call `Facter.clear` to
clear any cached values between examples.  This is a problem because
this behavior is not the concern of the example groups, the behavior is
the concern of the spec_helper or whatever facility we have in place to
initialize the system for testing.

This patch fixes the problem by duplicating the logic in the Facter
spec_helper to ensure facts are cleared out before each example.

This patch requires the example groups to explicitly load the facts they
require if the fact name does not match the filename.
Prevent undefined method `split' for nil:NilClass with pe_foo_version facts

Without this patch the pe_major_version, pe_minor_version, and
pe_patch_version facts directly depend on the pe_version fact in a
manner that calls split directly on the return value.

This is a problem because Fact values are not always guaranteed to
return strings, or objects that respond to split.  This patch is a
defensive measure to ensure we're always calling the split method on a
string object.

If the Fact returns nil, this will be converted to an empty string
responding to split.
Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x

* haus-add_pe_facts_to_stdlib:
  Prevent undefined method `split' for nil:NilClass with pe_foo_version facts
  (maint) Clear all facts before each example
  Add spec tests for pe_version facts
  Add PE facts to stdlib
Merge branch '2.4.x'

* 2.4.x:
  Prevent undefined method `split' for nil:NilClass with pe_foo_version facts
  (maint) Clear all facts before each example
  Add spec tests for pe_version facts
  Add PE facts to stdlib

Conflicts:
	spec/spec_helper.rb
Revert "Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x"

This reverts commit 74e6411157b8df1af9a24c17971e3236f3096529, reversing
changes made to 417d219aa6e42f2a16af42c98aa063fc1d9d2ecd.

Here's why:

Actually... I just screwed this up.

I merged this new fact into 2.4.x but it's not fixing any bug. It's adding a
new fact, so this should go into master and we should release 2.5 since this is
new, backwards-compatible functionality.
Merge branch '2.4.x'

* 2.4.x:
  Revert "Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x"
Revert "Revert "Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x""

This reverts commit d6d23b495cda0e154b4e73982acc43e586564c0e.

Why?  Because this change set should actually be in master and our
merge-up process reverted the change set in master when I reverted from
2.4.x.

This patch reverts the revert, restoring the original change set.
Revert "Revert "Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x""

This reverts commit d6d23b495cda0e154b4e73982acc43e586564c0e.

This backwards-compatible additional functionality is targeted at the
next minor release.  There are already backwards-incompatible changes in
the master branch so we need to establish a new minor branch.
Merge branch '2.5.x'

* 2.5.x:
  Revert "Revert "Merge branch 'haus-add_pe_facts_to_stdlib' into 2.4.x""
Add function ensure_resource and defined_with_params

This commit adds 2 new functions with unit tests.

defined_with_params works similarily to puppet's defined
function, except it allows you to also specify a hash of
params. defined_with_params will return true if a resource
also exists that matches the specified type/title (just like
with defined) as well as all of the specified params.

ensure_resource is a function that basically combines defined_with_params
with create_resources to conditionally create resources only if the
specified resource (title, type, params) does not already exist.

These functions are created to serve as an alternative to using
defined as follows:

    if ! defined(Package['some_package']) {
      package { 'some_package': ensure => present,
    }

The issue with this usage is that there is no guarentee about
what parameters were set in the previous definition of the package
that made its way into the catalog.

ensure_resource could be used instead, as:

    ensure_resource('package', 'some_package', { 'ensure' => 'present' })

This will creat the package resources only if another resource does
not exist with the specified parameters.
Handle undef for parameter argument

This commit adds better handling of the case where
undef is passed as the parameter value.

This works by converting '' into []
Add better docs about duplicate resource failures

This commit adds better inline documentation
explaining how replicate resource definitions can
occur if the resource exists and does not have
matching parameters.
re-formatting

This commit refactors to ensure 80 character lines.
Merge branch 'maint/2.5.x/pick_pr86_ensure_resource' into maint/2.5.x/pick_compatible_new_functionality

* maint/2.5.x/pick_pr86_ensure_resource:
  re-formatting
  Add better docs about duplicate resource failures
  Handle undef for parameter argument
  Add function ensure_resource and defined_with_params
Explicitly load functions used by ensure_resource

The ensure_resource function actually calls two
other functions, create_resources and defined_with_param.

When calling Puppet functions from Ruby, you sometimes have
to load the functions manually if they have not been called
before.

This commit explicitly loads the functions that ensure_resource
depends on from within the function.
Merge branch 'maint/2.5.x/pick_explicitly_load_functions' into maint/2.5.x/pick_compatible_new_functionality

* maint/2.5.x/pick_explicitly_load_functions:
  Explicitly load functions used by ensure_resource
Merge branch 'maint/2.5.x/pick_compatible_new_functionality' into 2.5.x

* maint/2.5.x/pick_compatible_new_functionality:
  Explicitly load functions used by ensure_resource
  re-formatting
  Add better docs about duplicate resource failures
  Handle undef for parameter argument
  Add function ensure_resource and defined_with_params
Merge branch '2.5.x'

* 2.5.x:
  Explicitly load functions used by ensure_resource
  re-formatting
  Add better docs about duplicate resource failures
  Handle undef for parameter argument
  Add function ensure_resource and defined_with_params