title: Setting default MongoDb/Bson representation for all decimals to double
body: <p>I am helping to write a C# application to analyse financial data. Internally all the numbers are stored as decimal, however when we persist them to our mongodb database, we would like them to be stored as doubles, rather than strings.
  I know I can do this for individual fields by applying the <code>[BsonRepresentation(BsonType.Double)]</code> attribute to each decimal field, but I keep forgetting  when adding new decimal values.</p>
  
  <p>Is there any way of making this the default representation for all decimal numbers?</p>