Allow ExclusionStrategy by field value.

When implementing the ExclusionStrategy, in shouldSkip* methods we have access 
to the fields attributes but not the fields values.

Might be usefull to be able to filter based on some specific values. So the 
idea here is to enhance the ExclusionStrategy to pass not just FieldAttributes 
but also the source object itself.

Original issue reported on code.google.com by [e-mail] on 3 Jul 2012 at 6:30

[bentatham]

+1. I would be great to shrink the JSON and parsing time by having a default value that does not need to be serialized at all, and the parsing code knows what the value is.

[GoogleCodeExporter]

To me (nearly) two years of silence sound loud and clear.

I guess the project owners are busy elsewhere and Gson works good enough for 
them. There isn't much happening here in general.

Original comment by [e-mail] on 13 May 2014 at 3:23