Effects: Add support for effects of different instances of same class

[dummdidumm]

Fixes #1246

With this change, it is possible to add different instances of the same class to the effects and have them running:

class ConfigurableEffect {
  @Effect({ dispatch: false })
  doSth$ = timer(1000).pipe(
    tap(() => console.log(this.message))
  );

  constructor(private message: string) { }
}

@NgModule({
  imports: [BrowserModule, FormsModule, StoreModule.forRoot(() => true), EffectsModule.forRoot([])],
  declarations: [AppComponent, HelloComponent],
  bootstrap: [AppComponent]
})
export class AppModule {
  constructor(effectSources: EffectSources) {
    effectSources.addEffects(new ConfigurableEffect("configA"));
    effectSources.addEffects(new ConfigurableEffect("configB"));
    // -> this did not work before, second effects instance was never run
  }
}

EffectSources still filters out effects which are already running, so no danger of running the same effects instance multiple times.

[coveralls]

Coverage increased (+0.003%) to 88.618% when pulling 994326e on dummdidumm:bugfix/effects_instances into 4223ff9 on ngrx:master.

[timdeschryver]

I might be overlooking something but won't the following accomplish the same thing?

groupBy(source => source),

[dummdidumm]

You are completely right, thanks for noticing! I will update the PR.