OS Ceilometer API support

OpenStack Ceilometer API's support (Skeleton & meters/samples API)


open issues I need help with -
1. meters and samples can get query params, problem is they cant be sent as null/empty string since ceilometer fails. example - {"filter": "", "orderby": "", "limit": ""}
need a way to avoid sending empty query params 
2. for meters API -
currently I've created "MetersApi.listMeters(QueryOptions... options)" should I follow this notion or simplify it as
"MetersApi.listMeters(String filter)" where filter is a json filter as in item #1
3. note that MetersApiMockTest.testListMetersWithQuery is failing since I cant get the API to send the QueryOptions on POST, it always goes on the GET as query params. any help would be appritiated 
The `<repositories>` section can be removed since it is no longer necessary. I need to pull it out of the Heat pom too :+1: