FEATURE: Hide Reviewable scores, change score filter to Priority

We found score hard to understand. It is still there behind the scenes
for sorting purposes, but it is no longer shown.

You can now filter by minimum priority (low, med, high) instead of
score.

app/models/reviewable.rb

@@ -56,7 +56,7 @@ class Reviewable < ActiveRecord::Base
   end
 
   def self.default_visible
-    where("score >= ?", SiteSetting.min_score_default_visibility)
+    where("score >= ?", min_score_for_priority)
   end
 
   def self.valid_type?(type)
@@ -133,8 +133,8 @@ class Reviewable < ActiveRecord::Base
     sub_total = (ReviewableScore.user_flag_score(user) + type_bonus + take_action_bonus)
 
     # We can force a reviewable to hit the threshold, for example with queued posts
-    if force_review && sub_total < SiteSetting.min_score_default_visibility
-      sub_total = SiteSetting.min_score_default_visibility
+    if force_review && sub_total < Reviewable.min_score_for_priority
+      sub_total = Reviewable.min_score_for_priority
     end
 
     rs = reviewable_scores.new(
@@ -155,6 +155,17 @@ class Reviewable < ActiveRecord::Base
     rs
   end
 
+  def self.set_priorities(medium: nil, high: nil)
+    PluginStore.set('reviewables', 'priority_medium', medium) if medium
+    PluginStore.set('reviewables', 'priority_high', high) if high
+  end
+
+  def self.min_score_for_priority(priority = nil)
+    priority ||= SiteSetting.reviewable_default_visibility
+    return 0.0 unless ['medium', 'high'].include?(priority)
+    return PluginStore.get('reviewables', "priority_#{priority}").to_f
+  end
+
   def history
     reviewable_histories.order(:created_at)
   end
@@ -316,11 +327,10 @@ class Reviewable < ActiveRecord::Base
     type: nil,
     limit: nil,
     offset: nil,
-    min_score: nil,
+    priority: nil,
     username: nil
   )
-    min_score ||= SiteSetting.min_score_default_visibility
-
+    min_score = Reviewable.min_score_for_priority(priority)
     order = (status == :pending) ? 'score DESC, created_at DESC' : 'created_at DESC'
 
     if username.present?
@@ -335,7 +345,7 @@ class Reviewable < ActiveRecord::Base
     result = result.where(type: type) if type
     result = result.where(category_id: category_id) if category_id
     result = result.where(topic_id: topic_id) if topic_id
-    result = result.where("score >= ?", min_score) if min_score
+    result = result.where("score >= ?", min_score) if min_score > 0
 
     # If a reviewable doesn't have a target, allow us to filter on who created that reviewable.
     if user_id