Adds More Server-Side Filtering Options for sl cci list.

Examples:
    sl cci list --datacenter=dal05
    sl cci list --network=100 --cpu=2
    sl cci list --memory='>= 2048'
    sl cci list --tags=production,db

* CLI: Moves NestedDict to top-level utils module so the managers can use it.
* CLI: Adds to_dict() method to NestedDict since the XML-RPC library is too strict about types.
Removes private filtering option
Moves query_filter() to SoftLayer.utils