Add possibility to access component scope inside of 'transformer' function

[MaKCbIMKo]

This will allow to access any other property of component inside of transformation function, e.g:

@Input() public anotherInput: string;

@select$(['selector'], (obs$, inst) => obs$.filter(x => x.name === inst.anotherInput))
public selectedObs: Observable<any>;

Such changes, IMHO, is pretty easy and it has backward compatibility.

[e-schultz]

This is in v7.1.0 now which just got released, thanks!