CakeEmail class be able to setting custom email validation rule.

Some of Japanese cellphone carriers (NTT Docomo and KDDI au) introduced RFC violated mail addresses. Even they fixed it for new registration, they are still widely used.

eg. foo.[at]example.com, .bar[at]example.com, foo..bar[at]example.com

CakeEmail can't set these email address.

This patch be able to set email validation rule to CakeEmail class.

https://cakephp.lighthouseapp.com/projects/42648-cakephp/tickets/3891