Reduce number of items in feeds, optimize regeneration worker slightly,

make regeneration worker unique, (only schedule/execute once at a time)

Gemfile.lock

@@ -387,6 +387,13 @@ GEM
       connection_pool (~> 2.2, >= 2.2.0)
       rack-protection (>= 1.5.0)
       redis (~> 3.2, >= 3.2.1)
+    sidekiq-merger (0.0.11)
+      activesupport (>= 3.2, < 6)
+      concurrent-ruby (~> 1.0)
+      sidekiq (>= 3.4, < 5)
+    sidekiq-unique-jobs (4.0.18)
+      sidekiq (>= 2.6)
+      thor
     simple-navigation (4.0.3)
       activesupport (>= 2.3.2)
     simple_form (3.2.1)
@@ -510,6 +517,8 @@ DEPENDENCIES
   sass-rails (~> 5.0)
   sdoc (~> 0.4.0)
   sidekiq
+  sidekiq-merger
+  sidekiq-unique-jobs
   simple-navigation
   simple_form
   simplecov