Adding dollar signs or % to amounts

* Added number_or_percent helper to return the correct string
* Deliverable.labor_budget will now return 0.0 if it's nil

  #1274

app/models/fixed_deliverable.rb

@@ -22,7 +22,7 @@ class FixedDeliverable < Deliverable
   
   # Budget for the labor, excluding overhead, profit, and materials
   def labor_budget
-    return read_attribute(:fixed_cost)
+    return read_attribute(:fixed_cost) || 0.0
   end
 
 end

app/models/hourly_deliverable.rb

@@ -41,7 +41,7 @@ class HourlyDeliverable < Deliverable
   
   # Budget for the labor, excluding overhead, profit, and materials
   def labor_budget
-    return read_attribute(:cost_per_hour).to_f * read_attribute(:total_hours).to_f
+    return (read_attribute(:cost_per_hour).to_f * read_attribute(:total_hours).to_f) || 0.0
   end
 
 end