Add serveraliases to cgit vhost template

Allow for specifying ServerAlias entries in the apache
vhost for the cgit puppet module.
(vhost template section lifted from the puppetlabs-apache v0.0.4
vhost-default template).

Change-Id: If7c297247b9556458154e4d01a1e0165a25a14b5
Merge "Add serveraliases to cgit vhost template"