Refactor RestAdapterConstructor

Currently, the DefaultPipeFactory processes a PipeConfig objects and passes its results to the appropriate RestAdapter constructor.

Restadapter should have a constructor which does the processing.

We should also look at making more fields final.

//pseudocode
public RestAdapter(PipeConfig config) {
handleGson(config)
handleUrl(config)
handlePaging(config)
etc(config)
}