Optional vhost

This patch modifies the puppet::master class to make the automatically created apache::vhost for the puppetmaster optional. My motivation is to use more restrictive SSL protocol and cipher suite settings, but this is good for anyone who needs any kind of special vhost behaviour.

Docs and rspec changes included. But honestly I have no clue whether the rspec stuff is sufficient. 

(And for some reason the fixtures from puppet forge where silently failing to install on my dev environment. Go figure.)