(maint) Move local egrammar makefile tasks to main Rakefile
(maint) Move methods for creating downloaders to factory

Previously, the plugin_handler module was responsible for creating
downloaders and evaluating them. Since all of this happens within a
single method it is hard to test that the downloaders are created with
the correct set of properties. For example, we `ignore` source
permissions when downloading plugins, but we `use` source permissions
when downloading external facts, since those often contain scripts,
which must be executable.

This commit moves the logic for creating the downloaders to a factory
and updates the tests accordingly. As part of this change, the
PluginHandler module is changed to a class and is no longer mixed into
the Configurer.
(maint) Test that external fact syncing depends on external feature

Previously, the test was trying to verify that the downloader objects
were created with the correct arguments, and testing that the
downloader was evaluated twice (since the same downloader was used for
both pluginsync and facts).

However, the downloader_factory_spec now tests that downloader objects
are created correctly, e.g. based on Puppet[:plugindest], so it is not
necessary to repeat that here.

This commit modifies the test to ensure the Downloader#evaluate
methods are called for both downloader objects, and adds a test to
ensure we skip downloading facts if the external facts feature is
false.
(PUP-2994) Make validation of storeconfigs a runtime concern.
(PUP-2879) Add cryptdisks-udev to the services blacklist

Also this patch splits out the long line in upstart_spec.rb to be
one line per service, so more diff-friendly.
Merge pull request #2956 from kylog/issue/pup-2879/exclude-cryptdisks-udev

(PUP-2879) Add cryptdisks-udev to the services blacklist
Merge branch 'master' into puppet-4
Merge pull request #2953 from hlindberg/PUP-2994_validation-of-exported

(PUP-2994) Make validation of storeconfigs a runtime concern.
(PUP-3001) Revert future parser change removing dynamic scoped defaults

This reverts the change in PUP-867 by (again) calling the same 3x logic
for looking up defaults. The implementation of PUP-867 also added tests,
and one of those are now changed to reflect the changed behavior.
(docs) Clarify possible exit codes and behavior with negative exit codes on Windows
(PUP-2972) Remove += and -=

Previously the future parser supported += and -=. += was very similar to
the same operator that is in the current parser, but with a few
differences to make it consistent with the rest of the
language. The += operator no longer performed string concatenation and
instead acted like $a = $a + $b. The -= operator was added to complete
the set of operators available.

However, many people have been confused by these operators (even as they
exist in the current parser):

  * It looks like mutation, but the language does not have mutation
  * It looks like += from other languages, but doesn't behave like them
  * Shadowing a variable is something that needs to be explicit,
    otherwise it becomes confusing.

This removes += and -= from the future parser. They are still parsed,
but the validation step will issue errors if they are encountered.
Merge pull request #2957 from hlindberg/PUP-3001_revert-867-dynamic-scoped-defaults-removal

(PUP-3001) Revert future parser change removing dynamic scoped defaults
Merge pull request #2943 from jpartlow/maint/master/move-egrammar-make-to-rake

(maint) Move local egrammar makefile tasks to main Rakefile
(docs) Remove stale warning that Windows can't manage symlinks

Windows can manage symlinks, and we explain the limitations (extra permissions
needed, no-go on 2003) in the `ensure` attribute.
(PUP-2879) Add two nfsd-related upstart services to the blacklist
(PUP-2972) Improve error message for += and -=

The previous error message was very abrupt and didn't provide any kind
of guidance for the user. The new message for += and -= let's them know
that it is *no longer* supported and has a link to where they can get
more information.
Merge pull request #2958 from zaphod42/issue/master/pup-2972-remove-plussignment

(PUP-2972) Remove += and -=
Merge pull request #2959 from nfagerlund/docs_windows_symlink_straggler

(docs) Remove stale warning that Windows can't manage symlinks
Merge pull request #2960 from kylog/issue/pup-2879/add-more-services-to-blacklist

(PUP-2879) Add two nfsd-related upstart services to the blacklist
Merge pull request #2879 from nfagerlund/docs_exec_exitcodes_windows

(docs) Clarify possible exit codes and behavior with negative exit codes on Windows