* extension

`* as val` could be very useful for values replacement. Dot replacement already work.
```
@value * as val from 'path';
```
becomes
```
:import('path') {
  val: *;
  prop1: imported1
}
```
Will be expanded to
```
:import('path') {
  prop1: imported1;
  prop2: imported2;
  prop3: imported3
}
```

/cc @sokra @sullenor 