Make Varnish 4 a first-class template, add storage_type.

This will allow Varnish 3 or 4 to run in malloc mode.
Add validation for ::varnish::storage_type.
Malloc derp.
Fix validation if params are actually integers.
Make thread settings actually work on Varnish 4.
Allow changing vcl_reload.

This is important since Varnish 4 puts it in /usr/sbin instead of
/usr/bin.
Merge branch 'master' of github.com:phase2/puppet-varnish