CRM-15536 fixes - Scheduled reminders: Clarify "Limit to" and "Also include" UI to prevent user errors

https://issues.civicrm.org/jira/browse/CRM-15536
Entity dropdown fix
Merge pull request #4557 from monishdeb/CRM-15536

CRM-15536 fixes - Scheduled reminders: Clarify "Limit to" and "Also incl...