Add configuration of the mail subsystem to WildFly docs

[jamesnetherton]

I've been trying to track down info on how the WildFly mail subsystem can be configured. There's plenty of info to be found through Google but seemingly none whatsoever included with the WildFly documentation.

It'd been good to have a section on how the subsystem can be configured, how secure transports can be used etc.

I can raise an enhancement request on Jira if anyone thinks it is worthwhile. 

[ctomc]

Yes, it was my oversight, please create jira issue for it.

tnx