Change: Add cli-commands to manage accounts

Tags: accounts

COMMANDS:

* list, ls        List existing accounts
* add, create     Create a new account
* update          Make changes to an existing account
* remove, rm      Removes an existing account
* inspect         Show detailed data on an existing account
* help, h         Shows a list of commands or help for one command

https://github.com/owncloud/product/issues/115
