(Promela) Bugfix
(Util model) Attribute inherits from Attributable

Goal of this commit is to allow Attributes objects to store other
attributes. It is useful for example in the case of annotations are
added to an Actor:

    @annot(arg1="val1",arg2="val2") @annot2 myobject

become something like

    myobject.attributes = [
        Attribute(
            name="annot",
            attributes=[
                Attribute(name="arg1", stringValue="val1"),
                Attribute(name="arg2", stringValue="val2")
            ]
        ),
        Attribute(name="annot2")
    ]

in the resulting IR
(ir) Change the way Annotation are stored and serialized
(CEmbedded) Correct a bug
(workflow) Fix Xtext MWE 2 workflow with last 2.4 version

Add some comments to prepare future migrations
(CEmbedded) Fix the backend
Merge branch 'master' of https://github.com/orcc/orcc
(grammar) Allow annotations before an ExpressionCall
(C) Add return in schedule function when there are no Input nor Output
(c backend) Add BlockFor and InstTernary support

And minor fixes
Merge branch 'master' into hmpp_backend