Add local MultivaluedHashMap implementation

Add local MultivaluedHashMap implementation

Corresponding Carbon patch - https://git.opendaylight.org/gerrit/#/c/63054/

The JSONRestconfService implementation contains a local UriInfo
implementation, SimpleUriInfo, that uses a MultivaluedHashMap
implementation from javax.ws.rs.core. This class is provided by
the dependency used at compile time however, the runtime bundle
that provides the javax.ws.rs.core interfaces doesn't provide
MultivaluedHashMap. Therefore I added our own local MultivaluedHashMap
class based on the external one.

Change-Id: I4f260f27684659fd734581617f6fa2002a6cd78c
Author:     Sai MarapaReddy <sai.marapareddy@gmail.com>
Signed-off-by: Sai MarapaReddy <sai.marapareddy@gmail.com>