(PUP-987) Remove the Ruby DSL

This removes the deprecated Ruby DSL support. It also removes
deprecation checks; an attempt to use a .rb manifest somewhere will
simply fail in some undefined manner, just as if there was an attempt to
use some other arbitrary text file. Most likely a syntax error from the
parser if someone forced it to use a .rb file.
(PUP-987) Remove .rb from the list of manifest extensions to autoload

This removes .rb from the glob of files to autoload/import
(PUP-987) Remove mention of Ruby DSL from documentation comment
(PUP-987) Remove support for the @ruby_code block in catalog AST types

This removes the ability to define the logic of node, class and
resource AST by giving it a block of ruby code. This was only used by
the Ruby DSL API.
(PUP-987) Cleanup {} around .pp in path
(PUP-987) Remove test that ended up testing nothing but its own mocking

Removed test that ended up testing that the puppet parser does not barf
on an empty.rb file
(PUP-987) Remove additional references to ruby_code and .rb manifests

command_line.rb handled .rb manifests from the command line.
and resource/type.rb still had the ruby_code attribute.
Unit tests checked that the attribute existed (but nothing else).
Merge pull request #3049 from hlindberg/PUP-987_remove-ruby-dsl

(PUP-987) Remove th Ruby DSL