Added menu links for seeing lists of things, also updated install.txt

src/Plugin/Menu/SeeAllActorsMenuLink.php

@@ -0,0 +1,9 @@
+<?php
+namespace Drupal\opencase\Plugin\Menu;
+ 
+use Drupal\Core\Menu\MenuLinkDefault;
+ 
+/**
+ * Represents a menu link for seeing all actors of some type.
+ */
+class SeeAllActorsMenuLink extends MenuLinkDefault {}