jsonrpc: Make reactor clients 1st class objects

Also add support for batch requests, tests to come soon

Change-Id: I64e4dfeb4eece4a85a3c6d36324b1e00f366a1cd
Signed-off-by: Saggi Mizrahi <smizrahi@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11402
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>