Get OAuth grants for the specified service principal

• command: aad oauthgrant list -i|--clientId <clientId>
• clientId: ID of the client for which OAuth grants should be retrieved
• requires connection to AAD Graph

The information can be get from the following REST call:

GET https://graph.windows.net/myorganization/oauth2PermissionGrants?api-version=1.6&$filter=clientId eq '<clientId>'
authorization: Bearer eyJ0eXAiOiJKV1QiLCJh...

Requires #160 to be done first