Support for auto-completion of storage pool related APIs

[Pearl1594]

This PR attempts to fix: https://github.com/apache/cloudstack-cloudmonkey/issues/98

For most APIs where id points to storage pools, the auto-completion does not work i.e., it doesn't find the list of storage pools. Few examples of this include: updateStorageCapabilities, enableStorageMaintenance, cancelStorageMaintenance, etc

Similarly, APIs which have storageid as arguments, do not auto-complete to list the available storage pools. for example: list volumes storageid=...

[Pearl1594]

Yes @DaanHoogland this is ready for testing.