implement ability to programatically reset the cached Set of filters

lib/report/filter.rb

@@ -9,6 +9,10 @@ class Report::Filter
     @all ||= Set[]
   end
 
+  def self.reset!
+    @all = nil
+  end
+
   def self.all_grouped
     all.group_by { |f| f.applies_for }.to_a.sort { |a,b| a.first.to_s <=> b.first.to_s }
   end

lib/report/group_by.rb

@@ -12,6 +12,10 @@ class Report::GroupBy
     Set[engine::GroupBy::SingletonValue]
   end
 
+  def self.reset!
+    @all = nil
+  end
+
   def self.all_grouped
     all.group_by { |f| f.applies_for }.to_a.sort { |a,b| a.first.to_s <=> b.first.to_s }
   end