Add some more policy strings

Summary: Provides more helpful text, notabl on `bin/policy show`.

Test Plan: Ran `bin/policy show`.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7204

Author: epriestley

src/applications/policy/filter/PhabricatorPolicy.php

@@ -153,6 +153,25 @@ public function getExplanation($capability) {
             return pht('Other: %s', $this->getName());
         }
         break;
+      case PhabricatorPolicyCapability::CAN_EDIT:
+        switch ($this->getPHID()) {
+          case PhabricatorPolicies::POLICY_USER:
+            return pht('Editable by all logged in users.');
+          case PhabricatorPolicies::POLICY_ADMIN:
+            return pht('Editable by all administrators.');
+          case PhabricatorPolicies::POLICY_NOONE:
+            return pht('Not editable by default.');
+        }
+
+        switch ($this->getType()) {
+          case PhabricatorPolicyType::TYPE_PROJECT:
+            return pht(
+              'Editable by members of the project "%s".',
+              $this->getName());
+          case PhabricatorPolicyType::TYPE_MASKED:
+            return pht('Other: %s', $this->getName());
+        }
+        break;
     }