fix(moment date service): use locale format by default

[katebatura]

Please read and mark the following check list before creating a pull request:

• I read and followed the CONTRIBUTING.md guide.
• I read and followed the New Feature Checklist guide.

Short description of what this resolves:

When manually typing the date into the input field, the DatePicker uses the provided DateFormat.

How to use:

@NgModule({
  imports: [
    NbDatepickerModule.forRoot(),
    NbMomentDateModule,
    ...
  ],
  providers: [{provide: LOCALE_ID, useValue: 'ru-RU'}],
})

Closes #2080

[yggg]

Let's reuse this.parse. And please check other adapters implementations.