API: POST and PUT requests fail to populate params object.

Due to the multiread filter required for accessing the body of
post and put requests grails fails to populate the params object for
data contained in the request body.

This change concats this data into the existing (mostly empty) params
object after successfull session establishment.
Merge pull request #20 from ausaccessfed/feature/#20-populate-params-for-api-post-put

Populate params object for POST and PUT requests on API