Refactor tor

This MR does a few things to refactor our tor support:

1. Fixes exits so that they properly are disabled with older versions of tor
2. Splits the tor services into three different possible types (tor-relay, tor-exit and hidden-service)
3. Makes sure that different tor services are not possible configurations when they are not allowed

provider_base/services/_tor_common.json

+{
+  "tor": {
+    "type": "disabled",
+    "contacts": "= [provider.contacts['tor'] || provider.contacts.default].flatten",
+    "nickname": "= (self.name + secret(:tor_family)).sub('_','')[0..18]",
+    "family": "= nodes[:services => 'tor'][:environment => '!local'].field('tor.nickname').join(',')"
+  }
+}