[FIXED JENKINS-19501] - Added isFast() and additional resolve()

Just for review... 

I've added a new method to MailAddressResolver interface. It allows explicit specification of resolver's applicability to usage in UIs. 

Resolves https://issues.jenkins-ci.org/browse/JENKINS-19501
Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>