Improve Account & Billing Functionality

[dryink]

Some clouds support account hierarchies and various APIs for obtaining billing information. It would be nice if the AdminServices class had something like AccountSupport and BillingSupport added to it.

Example methods would be...
Account:
createAccount
deleteAccount
listAccounts
getAccount
enableAccount
suspendAccount
updateAccount
Billing:
listBillingHistory
getInvoice
getAccountSummary (provides dollar estimates for the given account for a current month)