CRM-14765 - CRM_Utils_System::createDefaultCrudLink

Add helper for creating hyperlinks to entities based on the
entity-type/entity-id/desired-action. The link is determined
by the entity's BAO or by hook.
Merge pull request #3389 from totten/master-default-crud-links

CRM-14765 - CRM_Utils_System::createDefaultCrudLink