Environment hosts conventions

[pun-ky]

Motivation of this to be able to easy reuse host names defined in one place
also in custom tasks scripting:

wttech/gradle-aem-multi#67
wttech/gradle-aem-multi#68

to be able to write: aem.environment.hosts.live.httpUrl instead of hardcoding same domain in multiple places

or aem.environment.hosts.author.httpUrl etc

[pun-ky]

Demo, live too detailed. Maybe better just 'publish' and treat first publish host as for tests

[pun-ky]

final DSL

aem {
        hosts {
            author("http://author.example.com")
            publish("http://demo.example.com") { tag("test") }
            publish("http://example.com") { tag("live") }
            other("http://dispatcher.example.com")
        }
}

then

aem.environment.hosts.publish.url (return first tagged "publish")
or
aem.environment.hosts.find("publish, "live").url