adding named resource registry classes

[adamleff]

This is a cosmetic change to give the anonymous registry classes names to make it a bit clearer where to look when debugging in Pry.

The registry will look more like this:

"apache_conf"=>Inspec::Resource::Registry::ApacheConf,
"apt"=>Inspec::Resource::Registry::Apt,
"ppa"=>Inspec::Resource::Registry::Ppa,
"audit_policy"=>Inspec::Resource::Registry::AuditPolicy,

... instead of this:

"apache_conf"=>#<Class:0x007f991d4a0fc0>,
"apt"=>#<Class:0x007f991d482e58>,
"ppa"=>#<Class:0x007f991d482228>,
"audit_policy"=>#<Class:0x007f991d4799e8>,

[arlimus]

This is an awesome improvement!! Thank you @adamleff 😄

[arlimus]

After adding a couple of tests, I noticed we'll need one more fix ^^ to get this cleared. Almost there...