'label' annotation for modules

[gavinking]

We need an annotation to specify a readable name for a module, for example:

"Module documentation blah blah ... "
label("Ceylon Collections API")
module ceylon.collection "1.3.3" {
    ...
}

This label would be used by Herd and other tools that work with modules.

Perhaps the annotation should be named labelled.

[gavinking]

I have implemented this on the 7193 branch. But it still needs proper support in Herd and the IDEs.

[gavinking]

I've merged this work, and added some support in the IDE. But we still need:

• to add support to Herd, which is now eclipse-archived/ceylon-herd#292.
• to add support to ceylon doc (I will do this next).

[gavinking]

Now done, except for the Herd support, for which there is an open issue. Closing.