Bug 827486, part 1: add JSImplementation extended attribute. r=bz
Bug 827486, part 2 - Refactor example class codegen into common base class. r=bz
Bug 827486, part 3 - add dependencies for CGBindingImplClass. r=bz
Bug 827486, part 4: copy parts of example generator to JS impl generator. r=bz
Bug 827486, part 5: add the main JS impl code gen. r=bz
Bug 827486, part 6 - generate headers and code for JS implemented WebIDL classes. r=bz
Bug 827486, part 7 - add basic code gen test. r=bz