Improve output from (primarily) security commands

* Fix a few missing EOLs on output, some in security, some in other commands
* Fix `check_grant_blockers` to discard the `error` tuple label from `verify_permissions` before adding the message to the collected errors
* Stop swallowing errors in `riak_core_console`
* Add success messages
* Translate errors in `riak_core_console`
* Drop problematic single-role clause for `add_grant`/`add_revoke`, was only used by unit tests, could result in an infinite loop if invoked incorrectly from shell
    * Fix corresponding unit tests
* Unintentionally drop some spurious whitespace