style: code cleanup
feat(Template): @Template replaces @Decorator(Directive.TRANSCLUDE_CHILDREN)

Backward compatibility breaks:

1- Transclusion syntax has changed:

Before:

    @Decorator(
        selector: '[ng-if]',
        children: Directive.TRANSCLUDE_CHILDREN,
        map: const {'.': 'mapping'},
        <other kv pairs>)

After:

    @Template(
        selector: '[ng-if]',
        map: const {'ng-if' : 'mapping'},
        <other kv pairs>)

2- Directive.children has been removed in favor of
Directive.compileChildren dor Directive.map

Before:

    - children: Directive.COMPILE_CHILDREN
    - children: Directive.IGNORE_CHILDREN
    - children: Directive.TRANSCLUDE_CHILDREN

After:

    - compileChildren: true
    - compileChildren: false
    - Use @Template (see the previous section)