Support top level class block about hypertest

[mchlrch]

Xtext ships some commonly used terminals [1] and our language is using these [2]. This is pragmatic and we can change once we need/want to.

The effect of using STRING for the name/id is that the name/id is in double-quotes and just a string without constraints on the content. This is maybe not what we want in the long run but good to get started. It allows us to play with both simple and URI identifiers. For URI identifiers, we would otherwise need to define a custom terminal instead. Once we need identifiers that are cross-referenceable, we will come back to this.

1: https://github.com/eclipse/xtext-core/blob/master/org.eclipse.xtext/src/org/eclipse/xtext/common/Terminals.xtext
2: https://github.com/zazuko/api-testing-dsl/blob/master/com.zazuko.apitesting.dsl/com.zazuko.apitesting.dsl/src/com/zazuko/apitesting/dsl/ApiTestingDsl.xtext#L1

[mchlrch]

On the DSL side, I used the default STRING terminal rule from Xtext for the name/id instead of defining a custom terminal rule:

With Class "http://schema.org/Person" {
}

generates ..

{
	"steps": [
		{
			"type": "Class",
			"classId": "http://schema.org/Person",
			"children": [
			]
		}
	]
}

[tpluscode]

On the DSL side, I used the default STRING terminal rule from Xtext for the name/id instead of defining a custom terminal rule:

I don't understand what that means :)