Add ruby-pwsh gem

See merge request !13

This patch adds the `ruby-pwsh` gem:

  https://github.com/puppetlabs/ruby-pwsh

This gem is used by the puppetlabs/powershell Puppet module, so we
need to install it in order to test code using that module. Without
it, the tests will fail with an error:

> Could not autoload puppet/provider/exec/powershell: cannot load such
> file -- ruby-pwsh

Update RubyGems

See merge request !12

This patch updates Gemfile.lock with the newest version of the
RubyGems.

Update gems

See merge request !11

Fix build error due to missing Docker

See merge request !10

To be able to use the `docker` command, we must extend the `.docker`
job from the CI helpers repository.

Update to use GitLab CI helpers

See merge request !9

Remove unused variables

See merge request !7

Update dependencies

See merge request !6

This patch bumps the version number of the various dependencies.

Allow modules to opt-in to strict variables

See merge request !5

Strict variables can be disabled in spec tests by setting
`STRICT_VARIABLES` to `no`. This is done by default for existing
modules, since many of them have strict variable errors in third-party
dependencies.

This patch allows us to opt-in to strict variables in modules which
support it.

Update installed gems

See merge request !4

This updates Puppet to version 6.1.0 and librarian-puppet to 3.0.0

Use Puppetfile.lock when installing external modules

See merge request !3

Split modules

See merge request !2

Now that the Puppet master fetches configuration from the new
configuration service, we should longer upload these files to the
master.

This patch adds support for uploading the configuration and external
modules to the Puppet configuration service.

This will allow us to reuse that code in multiple scripts

The order of elements in the URL was changed, so we need to update
this project to match the new order.

This patch enables uploading of modules to the Puppet configuration
service. This service will simplify deployment of Puppet masters.

We no longer run any Puppet jobs on Jenkins, so we no longer need to
support it. This simplifies the code slightly.

We have some modules that don't have a Rakefile -- skip the tests in
that case.

Add Docker & GitLab CI support

See merge request !1

Add a test to verify the presence of the environment variables, and
give an error message if they are missing.

Instead of installing whatever is the latest version, pin the Ruby
gems on a specific version. This ensures that we are running a consistent version of the dependencies.