CRM-17645 breaks viewing Option Groups in some cases

See http://civicrm.stackexchange.com/questions/10711/why-cant-i-access-option-groups.

I replicated this on one 4.7.4 instance but not another; I'm not 100% sure why it works in one case, but I know why it does NOT work.

CRM_Core_Page_Basic->action calls CRM_Case_BAO_Case::caseCount (line 294). Due to CRM-17645, caseCount now requires a CiviCase permission - but CiviCase might not even be enabled. It fails with the backtrace/error posted on SE.

It reveals a second relatively minor bug though: \Civi\Api\Subscriber\PermissionCheck->onApiAuthorize has a line:
{{ $permissions = implode(' and ', $permissions);}}

That should (maybe) be:
{{ $permissions = implode(' and ', $permissions[0]);}}

That will change the error to:
insufficient permission: access my cases and activities and access all cases and activities

instead of:
insufficient permission: Array

I'm not 100% sure how to handle the permissions issue. This seems like a hack-in-a-hack, but a permission check on the appropriate permissions before calling `caseCount` is in order.