(PUP-2711) Make manifest-directory load recursively

This changes the loaded of a manifest reference that is a directory
to include all .pp recursively in this directory. The content is
sorted so that all content of directory b comes before file c in its
parent directory (rule applied recursively).
(PUP-2711) Make recursive manifest parsing conditional to future parser

This makes the ability to load all .pp files under a manifest dir
recursively conditional to parser == future. (It will become the
standard in Puppet 4.0). This is done to avoid slurping in lots of files
in case users kept other files around in a subdirectory in the belief
that they would not be loaded. Thus making it harder to upgrade.

This also adds a test that runs for future parser.
(PUP-2711) Remove '*' without effect.
(PUP-2711) Change use of Dir.glob to PathPattern.glob
Merge pull request #2834 from hlindberg/PUP-2711_recursive-manifest-dir

(PUP-2711) Make manifest-directory load recursively when future parser is on